Genetics, a discipline of biology, is the science of heredity and variation in living organisms. Foundations of modern biology There are five unifying principles Science (from the Latin scientia, meaning " Knowledge " or "knowing" is the effort to discover, and increase human understanding Genetic diversity is a level of Biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species ^[1][2] The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding. Stone Age Paleolithic See also Paleolithic, Recent African Origin, Early Homo sapiens, Early human migrations "Paleolithic" This article focuses on selective breeding in domesticated animals However, the modern science of genetics, which seeks to understand the process of inheritance, only began with the work of Gregor Mendel in the mid-nineteenth century. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was ^[3] Although he did not know the physical basis for heredity, Mendel observed that organisms inherit traits in a discrete manner—these basic units of inheritance are now called genes. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance

DNA, the molecular basis for inheritance. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Each strand of DNA is a chain of nucleotides, matching each other in the center to form what look like rungs on a twisted ladder. Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group

Genes correspond to regions within DNA, a molecule composed of a chain of four different types of nucleotides—the sequence of these nucleotides is the genetic information organisms inherit. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group DNA naturally occurs in a double stranded form, with nucleotides on each strand complementary to each other. Each strand can act as a template for creating a new partner strand—this is the physical method for making copies of genes that can be inherited. DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules

The sequence of nucleotides in a gene is translated by cells to produce a chain of amino acids, creating proteins—the order of amino acids in a protein corresponds to the order of nucleotides in the gene. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl This is known as the genetic code. The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins The amino acids in a protein determine how it folds into a three-dimensional shape; this structure is, in turn, responsible for the protein's function. Proteins carry out almost all the functions needed for cells to live. A change to the DNA in a gene can change a protein's amino acids, changing its shape and function: this can have a dramatic effect in the cell and on the organism as a whole.

Although genetics plays a large role in the appearance and behavior of organisms, it is the combination of genetics with what an organism experiences that determines the ultimate outcome. For example, while genes play a role in determining a person's height, the nutrition and health that person experiences in childhood also have a large effect. Human height varies according to both "nature" and "nurture". Nutrition (also called nourishment or aliment) is the provision to cells and Organisms of the materials necessary (in the form of food to support Health is a state of complete physical mental and social well-being and not merely the absence of disease or infirmity

History

Main article: History of genetics

Morgan's observation of sex-linked inheritance of a mutation causing white eyes in Drosophila led him to the hypothesis that genes are located upon chromosomes. The history of Genetics is generally held to have started with the work of an Augustinian Monk, Gregor Mendel. Drosophila is a Genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies"

Although the science of genetics began with the work of Gregor Mendel in the mid-1800s, there were some theories of inheritance that preceded Mendel. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was A popular theory during Mendel's time was the concept of blending inheritance: the idea that individuals inherit a smooth blend of traits from their parents. In Darwin's time biologists held to the theory of blending inheritance -- an offspring was an average of its parents Mendel's work disproved this, showing that traits are composed of combinations of distinct genes rather than a continuous blend. Also popular at the time was the theory of inheritance of acquired characteristics: the belief that individuals inherit traits that have been strengthened in their parents. inheritance of acquired characters (or characteristics) is the hereditary mechanism by which changes in physiology acquired over the life of an organism (such as muscle enlarged This theory (commonly associated with Jean-Baptiste Lamarck) is now known to be wrong, the experiences of individuals do not affect the genes they pass to their children. Jean-Baptiste Pierre Antoine de Monet Chevalier de Lamarck ( August 1, 1744 &ndash December 18, 1829) was a French Soldier ^[4]

Mendelian and classical genetics

The modern science of genetics traces its roots to Gregor Johann Mendel, a German-Czech Augustinian monk and scientist who studied of the nature of inheritance in plants. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was MONK is a Monte Carlo software package for simulating nuclear processes particularly for the purpose of determining the neutron multiplication factor or k-effective In his paper "Versuche über Pflanzenhybriden" ("Experiments on Plant Hybridization"), presented in 1865 to the Brunn Natural History Society, Gregor Mendel traced the inheritance patterns of certain traits in pea plants and showed that they could be described mathematically. Written in 1865 by Gregor Mendel, Experiments on Plant Hybridization ( German: Versuche über Pflanzen-Hybriden) was the result after Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was ^[5] Although this pattern of inheritance could only be observed for a few traits, Mendel's work suggested that statistics was a useful tool for studying inheritance.

The importance of Mendel's work was not understood until early in the 1900s, after his death, when his research was re-discovered by other scientists working on similar problems. The word genetics itself was coined in 1905 by William Bateson, a proponent of Mendel's work. William Bateson ( Robin Hood's Bay, August 8 1861 &ndash February 8 1926 was a British Geneticist, a Fellow of St ^[6][7] (The adjective genetic, derived from the Greek word genno (γεννώ): to give birth, predates the noun and was first used in a biological sense in 1860. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly ^[8]) Bateson popularized the usage of the word genetics to describe the study of inheritance in his inaugural address to the Third International Conference on Plant Hybridization in London, England, in 1906. ^[9]

After the rediscovery of Mendel's work, scientists tried to discover which molecules in the cell were responsible for inheritance. In 1910 Thomas Hunt Morgan argued that genes are on chromosomes, based on observations of a sex-linked white eye mutation in fruit flies. Thomas Hunt Morgan ( September 25, 1866 &ndash December 4, 1945) was an American geneticist and embryologist. ^[10] In 1913 his student Alfred Sturtevant used the phenomenon of genetic linkage to show that genes are arranged linearly on the chromosome. Alfred Henry Sturtevant ( November 21, 1891 &ndash April 5, 1970) was an American Geneticist. Genetic linkage occurs when particular genetic loci or Alleles for genes are inherited jointly ^[11]

James D. Watson (pictured) and Francis Crick resolved the structure of DNA in 1953. Francis Harry Compton Crick OM FRS (8 June 1916 – 28 July 2004 Ph

Molecular genetics

Although genes were known to exist on chromosomes, (chromosomes are composed of both protein and DNA) scientists did not know which of these was responsible for inheritance. In 1928, Frederick Griffith discovered of the phenomenon of transformation (see Griffith's experiment): dead bacteria could transfer genetic material to "transform" other still-living bacteria. Frederick Griffith (1879 - 1941 was a British medical officer and geneticist. In Molecular biology, transformation is the genetic alteration of a cell resulting from the uptake genomic incorporation and expression of foreign Griffith's experiment, conducted in 1928 by Frederick Griffith, was one of the first experiments suggesting that bacteria are capable of transferring genetic information Sixteen years later, in 1944, Oswald Theodore Avery, Colin McLeod and Maclyn McCarty identified the molecule responsible for transformation as DNA. Oswald Theodore Avery ( October 21, 1877 &ndash 2 February, 1955) was a Canadian -born American Physician and Colin Munro MacLeod ( January 28, 1909 &mdash February 11, 1972) was a Canadian-American geneticist Maclyn McCarty ( South Bend Indiana, June 9 1911 &ndash January 2 2005) was an American Geneticist. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known ^[12] The Hershey-Chase experiment in 1952 also showed that DNA (rather than protein) was the genetic material of the viruses that infect bacteria, further evidence that DNA was the molecule responsible for inheritance. The Hershey-Chase experiments were a series of Experiments conducted in 1952 by Alfred Hershey and Martha Chase, confirming that DNA ^[13]

James D. Watson and Francis Crick solved the structure of DNA in 1953, using the X-ray crystallography work of Rosalind Franklin that indicated DNA had a helical structure (ie. Francis Harry Compton Crick OM FRS (8 June 1916 – 28 July 2004 Ph X-ray crystallography is a method of determining the arrangement of Atoms within a Crystal, in which a beam of X-rays strikes a crystal and scatters Rosalind Elsie Franklin ( 25 July, 1920 Notting Hill, London – 16 April, 1958 Chelsea London) was an A helix (pl helixes or helices) from the Greek word έλιξ, is a special kind of Space curve, i shaped like a corkscrew). ^[14][15] Their double-helix model had two strands of DNA with the nucleotides pointing inwards, each matching a complementary nucleotide on the other strand to form what looks like rungs on a twisted ladder. ^[16] This structure showed that genetic information exists in the sequence of nucleotides on each strand of DNA. The structure also suggested a simple method for duplication: if the strands are separated, new partner strands can be reconstructed for each based on the sequence of the old strand.

Although the structure of DNA showed how inheritance worked, it was still not known how DNA influenced the behavior of cells. In the following years scientists tried to understand how DNA controls the process of protein production. Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl It was discovered that the cell uses DNA as a template to create matching messenger RNA (a molecule with nucleotides, very similar to DNA). Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product The nucleotide sequence of a messenger RNA is used to create an amino acid sequence in protein; this translation between nucleotide and amino acid sequences is known as the genetic code. In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins

With this molecular understanding of inheritance, an explosion of research became possible. One important development was chain-termination DNA sequencing in 1977 by Frederick Sanger: this technology allows scientists to read the nucleotide sequence of a DNA molecule. The term DNA sequencing encompasses biochemical methods for determining the order of the Nucleotide bases Adenine, Guanine, Cytosine Frederick Sanger, OM, CH, CBE, FRS (born 13 August 1918) is an English biochemist and twice ^[17] In 1983 the polymerase chain reaction was developed by Kary Banks Mullis, providing an quick way to isolate and amplify a specific section of a DNA from a mixture. Kary Banks Mullis, PhD (born December 28, 1944) is an American biochemist and Nobel laureate ^[18] These and other techniques, through the pooled efforts of the Human Genome Project and parallel private effort by Celera Genomics, culminated in the sequencing of the human genome in 2003. The Human Genome Project (HGP was an international Scientific research project with a primary goal to determine the sequence of chemical base pairs which make up DNA Celera Genomics ( was formerly a business unit of the Applera Corporation, but was spun off in July 2008 to become an independent publicly traded company In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby ^[19]

Features of inheritance

Discrete inheritance and Mendel's laws

Main article: Mendelian inheritance

A Punnett square depicting a cross between two pea plants heterozygous for purple (B) and white (b) blossoms

At its most fundamental level, inheritance in organisms occurs by means of discrete traits, called genes. Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance ^[20] This property was first observed by Gregor Mendel, who studied the segregation of heritable traits in pea plants. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was A pea (inaccurately called a '''sweet pea''' by food distubutors is most commonly the small spherical Seed or the seed-pod of the Legume Pisum ^[5][21] In his experiments studying the trait for flower color, Mendel observed that the flowers of each pea plant were either purple or white—and never an intermediate between the two colors. These different, discrete versions of the same gene are called alleles. An allele (ˈæliːl (UK /əˈliːl/ (US (from the Greek αλληλος allelos, meaning each other) is one member of a pair or series of different forms

In the case of pea plants, each organism has two alleles of each gene, and the plants inherit one allele from each parent. ^[22] Many organisms, including humans, have this pattern of inheritance. Organisms with two copies of the same allele are called homozygous, while organisms with two different alleles are heterozygous. Zygosity refers to the genetic condition of a Zygote. In genetics zygosity describes the similarity or dissimilarity of DNA between Homologous Zygosity refers to the genetic condition of a Zygote. In genetics zygosity describes the similarity or dissimilarity of DNA between Homologous

The set of alleles for a given organism is called its genotype, while the observable trait the organism has is called its phenotype. The genotype is the genetic constitution of a cell an organism or an individual (i A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties When organisms are heterozygous, often one allele is called dominant as its qualities dominate the phenotype of the organism, while the other allele is called recessive as its qualities recede and are not observed. Some alleles do not have complete dominance and instead have incomplete dominance by expressing an intermediate phenotype, or codominance by expressing both alleles at once. ^[23]

When a pair of organisms reproduce sexually, their offspring randomly inherit one of the two alleles from each parent. The Evolution of sexual reproduction is a major puzzle The first Fossilized evidence of sexually reproducing Organisms is from Eukaryotes of the Stenian These observations of discrete inheritance and the segregation of alleles are collectively known as Mendel's first law or the Law of Segregation. Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent

Genetic pedigree charts help track the inheritance patterns of traits.

Notation and diagrams

Geneticists use diagrams and symbols to describe inheritance. A gene is represented by a letter (or letters)—the capitalized letter represents the dominant allele and the recessive is represented by lowercase. ^[24] Often a "+" symbol is used to mark the usual, non-mutant allele for a gene.

In fertilization and breeding experiments (and especially when discussing Mendel's) the parents are referred to as the "P" generation and the offspring as the "F1" (first filial) generation. When the F1 offspring mate with each other, the offspring are called the "F2" (second filial) generation. One of the common diagrams used to predict the result of cross-breeding is the Punnett square. The Punnett square is a diagram that is used to predict the outcome of a particular cross or breeding experiment

When studying human genetic diseases, geneticists often use pedigree charts to represent the inheritance of traits. A Pedigree Chart is a chart which tells someone all of the known Phenotypes for an Organism and its Ancestors most commonly humans show Dogs ^[25] These charts map the inheritance of a trait in a family tree.

Interactions of multiple genes

Human height is a complex genetic trait. Francis Galton's data from 1889 shows the relationship between offspring height as a function of mean parent height. Sir Francis Galton FRS ( 16 February 1822 &ndash 17 January 1911) half-cousin of Charles Darwin, was an While correlated, remaining variation in offspring heights indicates environment is also an important factor in this trait.

Organisms have thousands of genes, and in sexually reproducing organisms assortment of these genes are generally independent of each other. This means that the inheritance of an allele for yellow or green pea color is unrelated to the inheritance of alleles for white or purple flowers. This phenomenon, known as "Mendel's second law" or the "Law of independent assortment", means that the alleles of different genes get shuffled between parents to form offspring with many different combinations. Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent (Some genes do not assort independently, demonstrating genetic linkage, a topic discussed later in this article. Genetic linkage occurs when particular genetic loci or Alleles for genes are inherited jointly )

Often different genes can interact in a way that influences the same trait. In the Blue-eyed Mary (Omphalodes verna), for example, there exists a gene with alleles that determine the color of flowers: blue or magenta. The Blue-eyed Mary or Navelwort ( Omphalodes verna) is a perennial plant native to Central and South-east Europe Another gene, however, controls whether the flowers have color at all: color or white. When a plant has two copies of this white allele, its flowers are white—regardless of whether the first gene has blue or magenta alleles. This interaction between genes is called epistasis, with the second gene epistatic to the first. Epistasis is the Interaction between genes Epistasis takes place when the action of one Gene is modified by one or several other genes which are sometimes called ^[26]

Many traits are not discrete features (eg. purple or white flowers) but are instead continuous features (eg. human height and skin color). These complex traits are the product of many genes. Inheritance of quantitative traits or polygenic inheritance refers to the inheritance of a phenotypic characteristic that varies in degree and can be attributed to ^[27] The influence of these genes is mediated, to varying degrees, by the environment an organism has experienced. The degree to which an organism's genes contribute to a complex trait is called heritability. In Genetics, Heritability is the proportion of phenotypic variation in a population that is attributable to genetic variation among individuals ^[28] Measurement of the heritability of a trait is relative—in a more variable environment, the environment has a bigger influence on the total variation of the trait. For example, human height is a complex trait with a heritability of 89% in the United States. In Nigeria, however, where people experience a more variable access to good nutrition and health care, height has a heritability of only 62%. ^[29]

Molecular basis for inheritance

DNA and chromosomes

Main articles: DNA and Chromosome

The molecular structure of DNA. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known A chromosome is an organized structure of DNA and Protein that is found in cells. Molecular geometry or molecular structure is the three- Dimensional arrangement of the Atoms that constitute a Molecule. Bases pair through the arrangement of hydrogen bonding between the strands. A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen

The molecular basis for genes is deoxyribonucleic acid (DNA). In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known DNA is composed of a chain of nucleotides, of which there are four types: adenine (A), cytosine (C), guanine (G), and thymine (T). Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group Adenine is a Purine with a variety of roles in Biochemistry including Cellular respiration, in the form of both the energy-rich Adenosine Cytosine is one of the five main bases found in DNA and RNA. It is a Pyrimidine derivative with a Heterocyclic Aromatic ring Guanine is one of the five main Nucleobases found in the Nucleic acids DNA and RNA, the others being Adenine, Cytosine, Thymine is one of the four bases in the Nucleic acid of DNA that make up the letters ATGC Genetic information exists in the sequence of these nucleotides, and genes exist as stretches of sequence along the DNA chain. ^[30] Viruses are the only exception to this rule—sometimes viruses use the very similar molecule RNA instead of DNA as their genetic material. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known ^[31]

DNA normally exists as a double-stranded molecule, coiled into the shape of a double-helix. In Geometry a double helix (plural helices) typically consists of two congruent helices with the same axis differing by a translation Each nucleotide in DNA preferentially pairs with its partner nucleotide on the opposite strand: A pairs with T, and C pairs with G. Thus, in its two-stranded form, each strand effectively contains all necessary information, redundant with its partner strand. This structure of DNA is the physical basis for inheritance: DNA replication duplicates the genetic information by splitting the strands and using each strand as a template for synthesis of a new partner strand. DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules ^[32]

Genes are arranged linearly along long chains of DNA sequence, called chromosomes. A chromosome is an organized structure of DNA and Protein that is found in cells. In bacteria, each cell has a single circular chromosome, while eukaryotic organisms (which includes plants and animals) have their DNA arranged in multiple linear chromosomes. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex These DNA strands are often extremely long; the largest human chromosome, for example, is about 247 million base pairs in length. In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called ^[33] The DNA of a chromosome is associated with structural proteins that organize, compact, and control access to the DNA, forming a material called chromatin; in eukaryotes chromatin is usually composed of nucleosomes, repeating units of DNA wound around a core of histone proteins. Chromatin is the complex basis of DNA and protein that makes up Chromosomes It is found inside the nuclei of eukaryotic cells, and within the Chromatin is the complex basis of DNA and protein that makes up Chromosomes It is found inside the nuclei of eukaryotic cells, and within the Nucleosomes form the fundamental repeating units of eukaryotic Chromatin, which is used to pack the large eukaryotic genomes into the nucleus while still ensuring In Biology, histones are the chief Protein components of Chromatin. ^[34] The full set of hereditary material in an organism (usually the combined DNA sequences of all chromosomes) is called the genome. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby

While haploid organisms have only one copy of each chromosome, most animals and many plants are diploid, containing two of each chromosome and thus two copies of every gene. "Haplo" redirects here For the fictional character see The Death Gate Cycle. "Haplo" redirects here For the fictional character see The Death Gate Cycle. ^[35] The two alleles for a gene are located on identical loci of sister chromatids, each allele inherited from a different parent. In the fields of Genetics and Evolutionary computation, a locus (plural loci) is a fixed position on a Chromosome such as the position of a A chromatid is one of two identical copies of DNA making up a replicated Chromosome, which are joined at their Centromeres for the process of Cell division

Walther Flemming's 1882 diagram of eukaryotic cell division. Walther Flemming ( April 21[[ 843]] - August 4[[ 905]] was a German Biologist and the founder of Cytogenetics. Chromosomes are copied, condensed, and organized. Then, as the cell divides, chromosome copies separate into the daughter cells.

An exception exists in the sex chromosomes, specialized chromosomes many animals have evolved that play a role in determining the sex of an organism. A sex-determination system is a biological system that determines the development of sexual characteristics in an Organism. ^[36] In humans and other mammals the Y chromosome has very few genes and triggers the development of male sexual characteristics, while the X chromosome is similar to the other chromosomes and contains many genes unrelated to sex determination. Females have two copies of the X chromosome, but males have one Y and only one X chromosome—this difference in X chromosome copy numbers leads to the unusual inheritance patterns of sex-linked disorders. Sex linkage is the phenotypic expression of an Allele that is related to the chromosomal sex of the individual

Reproduction

Main articles: Asexual reproduction and Sexual reproduction

When cells divide, their full genome is copied and each daughter cell inherits one copy. Asexual reproduction is a form of reproduction which does not involve Meiosis, Ploidy reduction or Fertilization. The Evolution of sexual reproduction is a major puzzle The first Fossilized evidence of sexually reproducing Organisms is from Eukaryotes of the Stenian This process, called mitosis, is the simplest form of reproduction and is the basis for asexual reproduction. Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei Asexual reproduction is a form of reproduction which does not involve Meiosis, Ploidy reduction or Fertilization. Asexual reproduction can also occur in multicellular organisms, producing offspring that inherit their genome from a single parent. Offspring that are genetically identical to their parents are called clones. This page refers to the Irish town For other uses see Clones (disambiguation, or Clone Clones (Cluain Eois &ndash ˈkloʊnɪs

Eukaryotic organisms often use sexual reproduction to generate offspring that contain a mixture of genetic material inherited from two different parents. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex The Evolution of sexual reproduction is a major puzzle The first Fossilized evidence of sexually reproducing Organisms is from Eukaryotes of the Stenian The process of sexual reproduction alternates between forms that contain single copies of the genome (haploid) and double copies (diploid). "Haplo" redirects here For the fictional character see The Death Gate Cycle. "Haplo" redirects here For the fictional character see The Death Gate Cycle. ^[35] Haploid cells fuse and combine genetic material to create a diploid cell with paired chromosomes. Diploid organisms form haploids by dividing, without replicating their DNA, to create daughter cells that randomly inherit one of each pair of chromosomes. Most animals and many plants are diploid for most of their lifespan, with the haploid form reduced to single cell gametes. A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete

Although they do not use the haploid/diploid method of sexual reproduction, bacteria have many methods of acquiring new genetic information. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Some bacteria can undergo conjugation, transferring a small circular piece of DNA to another bacterium. Bacterial conjugation is the transfer of genetic material between bacteria through direct cell-to-cell contact ^[37] Bacteria can also take up raw DNA fragments found in the environment and integrate them into their genome, a phenomenon known as transformation. In Molecular biology, transformation is the genetic alteration of a cell resulting from the uptake genomic incorporation and expression of foreign ^[38] This processes result in horizontal gene transfer, transmitting fragments of genetic information between organisms that would otherwise be unrelated.

Thomas Hunt Morgan's 1916 illustration of a double crossover between chromosomes

Recombination and linkage

Main articles: Chromosomal crossover and Genetic linkage

The diploid nature of chromosomes allows for genes on different chromosomes to assort independently during sexual reproduction, recombining to form new combinations of genes. Thomas Hunt Morgan ( September 25, 1866 &ndash December 4, 1945) was an American geneticist and embryologist. Genetic linkage occurs when particular genetic loci or Alleles for genes are inherited jointly Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent Genes on the same chromosome would theoretically never recombine, however, were it not for the process of chromosomal crossover. During crossover, chromosomes exchange stretches of DNA, effectively shuffling the gene alleles between the chromosomes. ^[39] This process of chromosomal crossover generally occurs during meiosis, a series of cell divisions that creates haploid germ cells that later combine with other germ cells to form child organisms. In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half Germ cells are progenitors of the Gametes. These singled out cells move through the gut to the developing Gonads and undergo mitotic proliferation followed

The probability of chromosomal crossover occurring between two given points on the chromosome is related to the distance between them. For an arbitrarily long distance, the probability of crossover is high enough that the inheritance of the genes is effectively uncorrelated. For genes that are closer together, however, the lower probability of crossover means that the genes demonstrate genetic linkage—alleles for the two genes tend to be inherited together. Genetic linkage occurs when particular genetic loci or Alleles for genes are inherited jointly The amounts of linkage between a series of genes can be combined to form a linear linkage map that roughly describes the arrangement of the genes along the chromosome. Genetic linkage occurs when particular genetic loci or Alleles for genes are inherited jointly ^[40]

Gene expression

The genetic code: DNA, through a messenger RNA intermediate, codes for protein with a triplet code. The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product

Genetic code

Main article: Genetic code

Genes generally express their functional effect through the production of proteins, which are complex molecules responsible for most functions in the cell. The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Proteins are chains of amino acids, and the DNA sequence of a gene (through an RNA intermediate) is used to produce a specific protein sequence. In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this This process begins with the production of an RNA molecule with a sequence matching the gene's DNA sequence, a process called transcription. Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units Transcription is the synthesis of RNA under the direction of DNA

This messenger RNA molecule is then used to produce a corresponding amino acid sequence through a process called translation. Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product Translation is the first stage of Protein biosynthesis (part of the overall process of Gene expression) Each group of three nucleotides in the sequence, called a codon, corresponds to one of the twenty possible amino acids in protein—this correspondence is called the genetic code. The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins The genetic code is the set of rules by which information encoded in genetic material ( DNA or RNA sequences is translated into Proteins ^[41] The flow of information is unidirectional: information is transferred from nucleotide sequences into the amino acid sequence of proteins, but never from protein back into the sequence of DNA—a phenomenon Francis Crick called the central dogma of molecular biology. Francis Harry Compton Crick OM FRS (8 June 1916 – 28 July 2004 Ph The central dogma of molecular biology was first enunciated by Francis Crick in 1958 and re-stated in a Nature paper published in 1970 ^[42]

The dynamic structure of hemoglobin is responsible for its ability to transport oxygen within mammalian blood.

A single amino acid change causes hemoglobin to form fibers.

The specific sequence of amino acids results in a unique three-dimensional structure for that protein, and the three-dimensional structures of protein are related to their function. Protein folding is the physical process by which a Polypeptide folds into its characteristic and functional three-dimensional structure. ^[43][44] Some are simple structural molecules, like the fibers formed by the protein collagen. Collagen is the main Protein of Connective tissue in Animals and the most abundant protein in Mammals making up about 50% of the whole-body protein Proteins can bind to other proteins and simple molecules, sometimes acting as enzymes by facilitating chemical reactions within the bound molecules (without changing the structure of the protein itself). Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Protein structure is dynamic; the protein hemoglobin bends into slightly different forms as it facilitates the capture, transport, and release of oxygen molecules within mammalian blood. Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein

A single nucleotide difference within DNA can cause a single change in the amino acid sequence of a protein. Because protein structures are the result of their amino acid sequences, some changes can dramatically change the properties of a protein by destabilizing the structure or changing the surface of the protein in a way that changes its interaction with other proteins and molecules. For example, sickle-cell anemia is a human genetic disease that results from a single base difference within the coding region for the β-globin section of hemoglobin, causing a single amino acid change that changes hemoglobin's physical properties. Sickle-cell disease or sickle-cell anaemia (or anemia) is a Blood disorder characterized by Red blood cells that assume an abnormal rigid ^[45] Sickle-cell versions of hemoglobin stick to themselves, stacking to form fibers that distort the shape of red blood cells carrying the protein. These sickle-shaped cells no longer flow smoothly through blood vessels, having a tendency to clog or degrade, causing the medical problems associated with the disease.

Some genes are transcribed into RNA but are not translated into protein products—these are called non-coding RNA molecules. A non-coding RNA ( ncRNA) is any RNA molecule that is not translated into a Protein. In some cases these products fold into structures which are involved in critical cell functions (eg. ribosomal RNA and transfer RNA). Ribosomal RNA ( rRNA) is the central component of the Ribosome, the protein manufacturing machinery of all living cells. Transfer RNA (abbreviated tRNA) is a small RNA (usually about 74-95 nucleotides that transfers a specific Amino acid to a growing polypeptide chain at RNA can also have regulatory effect through hybridization interactions with other RNA molecules (eg. microRNA). In Genetics, microRNAs ( miRNA) are single-stranded RNA molecules of about 21–23 Nucleotides in length which regulate Gene expression

Nature vs. nurture

Although genes contain all the information an organism uses to function, the environment plays an important role in determining the ultimate phenotype—a dichotomy often referred to as "nature vs. nurture. The nature versus nurture debates concern the relative importance of an individual's innate qualities ("nature" i " The phenotype of an organism depends on the interaction of genetics with the environment. One example of this is the case of temperature-sensitive mutations. Often, a single amino acid change within the sequence of a protein does not change its behavior and interactions with other molecules, but it does destabilize the structure. In a high temperature environment, where molecules are moving more quickly and hitting each other, this results in the protein losing its structure and failing to function. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Denaturation is a process in which Proteins or Nucleic acids lose their structure (tertiary structure by application of some external stress or compound for In a low temperature environment, however, the protein's structure is stable and functions normally. This type of mutation is visible in the coat coloration of Siamese cats, where a mutation in an enzyme responsible for pigment production causes it to destabilize and lose function at high temperatures. The Siamese is one of the first distinctly recognised breeds of Oriental Cat. ^[46] The protein remains functional in areas of skin that are colder—legs, ears, tail, and face—and so the cat has dark fur at its extremities.

Siamese cats have a temperature-sensitive mutation in pigment production.

Environment also plays a dramatic role in effects of the human genetic disease phenylketonuria. Phenylketonuria ( PKU) is an Autosomal recessive Genetic disorder characterized by a deficiency in the enzyme Phenylalanine hydroxylase ^[47] The mutation that causes phenylketonuria disrupts the ability of the body to break down the amino acid phenylalanine, causing a toxic build-up of an intermediate molecule that, in turn, causes severe symptoms of progressive mental retardation and seizures. Phe redirects here For the BitTorrent feature see PHE. For the constellation see Phoenix (constellation. If someone with the phenylketonuria mutation follows a strict diet that avoids this amino acid, however, they remain normal and healthy.

Gene regulation

Main article: Regulation of gene expression

The genome of a given organism contains thousands of genes, but not all these genes need to be active at any given moment. Gene modulation redirects here For information on therapeutic regulation of gene expression see Therapeutic gene modulation. A gene is expressed when it is being transcribed into mRNA (and translated into protein), and there exist many cellular methods of controlling the expression of genes such that proteins are produced only when needed by the cell. Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such Transcription factors are regulatory proteins that bind to the start of genes, either promoting or inhibiting the transcription of the gene. In the field of Molecular biology, a transcription factor (sometimes called a sequence-specific DNA binding factor is a Protein that binds to specific sequences ^[48] Within the genome of Escherichia coli bacteria, for example, there exists a series of genes necessary for the synthesis of the amino acid tryptophan. Tryptophan (abbreviated as Trp or W) is one of the 20 standard amino acids, as well as an Essential amino acid in the Human diet However, when tryptophan is already available to the cell, these genes for tryptophan synthesis are no longer needed. The presence of tryptophan directly affects the activity of the genes—tryptophan molecules bind to the tryptophan repressor (a transcription factor), changing the repressor's structure such that the repressor binds to the genes. The trp (tryptophan repressor is a 25 kD Protein which regulates transcription of the Tryptophan biosynthetic pathway in Bacteria. The tryptophan repressor blocks the transcription and expression of the genes, thereby creating negative feedback regulation of the tryptophan synthesis process. Negative Feedback feeds part of a System 's output inverted into the system's input generally with the result that fluctuations are attenuated ^[49]

Transcription factors bind to DNA, influencing the transcription of associated genes.

Differences in gene expression are especially clear within multicellular organisms, where cells all contain the same genome but have very different structures and behaviors due to the expression of different sets of genes. Multicellular organisms are Organisms consisting of more than one cell, and having Differentiated cells that perform specialized functions All the cells in a multicellular organism derive from a single cell, differentiating into different cell types in response to external and intercellular signals and gradually establishing different patterns of gene expression to create different behaviors. Cell signaling is part of a Complex system of Communication that governs basic cellular activities and coordinates cell actions No single gene is responsible for the development of structures within multicellular organisms, these patterns arise from the complex interactions between many cells. MOrphogenesis is an EP by Industrial Black metal band.And Oceans.

Within eukaryotes there exist structural features of chromatin that influence the transcription of genes, often in the form of modifications to DNA and chromatin that are stably inherited by daughter cells. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Chromatin is the complex basis of DNA and protein that makes up Chromosomes It is found inside the nuclei of eukaryotic cells, and within the ^[50] These features are called "epigenetic" because they exist "on top" of the DNA sequence and retain inheritance from one cell generation to the next. In Biology, the term epigenetics refers to changes in Gene expression caused by mechanisms other than changes in the underlying DNA sequence Because of epigenetic features, different cell types grown within the same medium can retain very different properties. Cell culture is the process by which prokaryotic, or eukaryotic cells are grown under controlled conditions Although epigenetic features are generally dynamic over the course of development, some, like the phenomenon of paramutation, have multigenerational inheritance and exist as rare exceptions to the general rule of DNA as the basis for inheritance. In Epigenetics, paramutation is an interaction between two Alleles of a single locus, resulting in a heritable change of one allele that is induced by the ^[51]

Genetic change

Gene duplication allows diversification by providing redundancy: one gene can mutate and lose its original function without harming the organism.

Mutations

Main article: Mutation

During the process of DNA replication, errors occasionally occur in the polymerization of the second strand. In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules These errors, called mutations, can have an impact on the phenotype of an organism, especially if they occur within the protein coding sequence of a gene. In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism Error rates are usually very low—1 error in every 10–100 million bases—due to the "proofreading" ability of DNA polymerases. ^[52][53] (Without proofreading error rates are a thousand-fold higher; because many viruses rely on DNA and RNA polymerases that lack proofreading ability, they experience higher mutation rates. ) Processes that increase the rate of changes in DNA are called mutagenic: mutagenic chemicals promote errors in DNA replication, often by interfering with the structure of base-pairing, while UV radiation induces mutations by causing damage to the DNA structure. In Biology, a mutagen ( Latin, literally origin of change) is a physical or chemical agent that changes the genetic information (usually DNA) Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays ^[54] Chemical damage to DNA occurs naturally as well, and cells use DNA repair mechanisms to repair mismatches and breaks in DNA—nevertheless, the repair sometimes fails to return the DNA to its original sequence. DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome.

In organisms that use chromosomal crossover to exchange DNA and recombine genes, errors in alignment during meiosis can also cause mutations. In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half ^[55] Errors in crossover are especially likely when similar sequences cause partner chromosomes to adopt a mistaken alignment; this makes some regions in genomes more prone to mutating in this way. These errors create large structural changes in DNA sequence—duplications, inversions or deletions of entire regions, or the accidental exchanging of whole parts between different chromosomes (called translocation). Gene duplication (or chromosomal duplication) is any duplication of a region of DNA that contains a Gene; it may occur as an error in Homologous An inversion is a Chromosome rearrangement in which a segment of a chromosome is reversed end to end In Genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) is a Mutation (a genetic aberration In Genetics, a chromosome translocation is a Chromosome abnormality caused by rearrangement of parts between nonhomologous Chromosomes.

Natural selection and evolution

Main article: Evolution

Mutations produce organisms with different genotypes, and those differences can result in different phenotypes. eVolution is the third Album by eLDee, it was due to be released in 2008 Many mutations have little effect on an organism's phenotype, health, and reproductive fitness. Fitness (often denoted w in Population genetics models is a central concept in evolutionary theory. Mutations that do have an effect are often deleterious, but occasionally mutations are beneficial.

An evolutionary tree of eukaryotic organisms, constructed by comparison of several orthologous gene sequences

Population genetics research studies the distributions of these genetic differences within populations and how the distributions change over time. A phylogenetic tree, also called an evolutionary tree, is a tree showing the Evolutionary relationships among various biological Species or other In Evolutionary biology, homology has come to mean any similarity between characters that is due to their shared ancestry. Population genetics is the study of the Allele frequency distribution and change under the influence of the four evolutionary forces Natural selection, Genetic ^[56] Changes in the frequency of an allele in a population can be influenced by natural selection, where a given allele's higher rate of survival and reproduction causes it to become more frequent in the population over time. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of ^[57] Genetic drift can also occur, where chance events lead to random changes in allele frequency. In Population genetics, genetic drift is the accumulation of random events that change the makeup of a gene pool slightly but often compound over time ^[58]

Over many generations, the genomes of organisms can change, resulting in the phenomenon of evolution. eVolution is the third Album by eLDee, it was due to be released in 2008 Mutations and the selection for beneficial mutations can cause a species to evolve into forms that better survive their environment, a process called adaptation. eVolution is the third Album by eLDee, it was due to be released in 2008 An adaptation is a characteristic of an Organism that has been favored by Natural selection and ^[59] New species are formed through the process of speciation, a process often caused by geographical separations that allow different populations to genetically diverge. Speciation is the Evolutionary process by which new biological Species arise ^[60]

As sequences diverge and change during the process of evolution, these differences between sequences can be used as a molecular clock to calculate the evolutionary distance between them. The molecular clock (based on the molecular clock hypothesis ( MCH) is a technique in Molecular evolution to relate the divergence time of two Species ^[61] Genetic comparisons are generally considered the most accurate method of characterizing the relatedness between species, an improvement over the sometimes deceptive comparison of phenotypic characteristics. The evolutionary distances between species can be combined to form evolutionary trees—these trees represent the common descent and divergence of species over time, although they cannot represent the transfer of genetic material between unrelated species (known as horizontal gene transfer and most common in bacteria). A phylogenetic tree, also called an evolutionary tree, is a tree showing the Evolutionary relationships among various biological Species or other A group of organisms is said to have common descent if they have a common Ancestor.

Research and technology

The common fruit fly (Drosophila melanogaster) is a popular model organism in genetics research. Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a two-winged insect that belongs to the Diptera, the order A model organism is a Species that is extensively studied to understand particular biological Phenomena, with the expectation that discoveries made

Model organisms and genetics

Although geneticists originally studied inheritance in a wide range of organisms, researchers began to specialize in studying the genetics of a particular subset of organisms. The fact that significant research already existed for a given organism would encourage new researchers to choose it for further study, and so eventually a few model organisms became the basis for most genetics research. A model organism is a Species that is extensively studied to understand particular biological Phenomena, with the expectation that discoveries made ^[62] Common research topics in model organism genetics include the study of gene regulation and the involvement of genes in development and cancer. Gene modulation redirects here For information on therapeutic regulation of gene expression see Therapeutic gene modulation. MOrphogenesis is an EP by Industrial Black metal band.And Oceans. Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled

Organisms were chosen, in part, for convenience—short generation times and easy genetic manipulation made some organisms popular genetics research tools. Widely used model organisms include the gut bacterium Escherichia coli, the plant Arabidopsis thaliana, baker's yeast (Saccharomyces cerevisiae), the nematode Caenorhabditis elegans, the common fruit fly (Drosophila melanogaster), and the common house mouse (Mus musculus). Arabidopsis thaliana ( A-ra-bi-dóp-sis tha-li-á-na; thale cress, mouse-ear cress or Arabidopsis) is a small Saccharomyces cerevisiae is a Species of Budding Yeast. It is perhaps the most useful Yeast owing to its use since ancient times Caenorhabditis elegans (ˌsiːnoʊræbˈdaɪtɪs ˈɛlɪgænz is a free-living Nematode (roundworm about 1  mm in length which Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a two-winged insect that belongs to the Diptera, the order The House Mouse ( Mus musculus) is one of the most numerous species of the genus Mus commonly termed a Mouse.

Medical genetics research

Medical genetics seeks to understand how genetic variation relates to human health and disease. Medical genetics is the specialty of Medicine that involves the diagnosis and management of Hereditary disorders Medical genetics differs from Human genetics ^[63] When searching for an unknown gene that may be involved in a disease, researchers commonly use genetic linkage and genetic pedigree charts to find the location on the genome associated with the disease. Genetic linkage occurs when particular genetic loci or Alleles for genes are inherited jointly A Pedigree Chart is a chart which tells someone all of the known Phenotypes for an Organism and its Ancestors most commonly humans show Dogs At the population level, researchers take advantage of Mendelian randomization to look for locations in the genome that are associated with diseases, a technique especially useful for multigenic traits not clearly defined by a single gene. In Epidemiology, Mendelian randomization is a method of using non-experimental studies to examine the causal effect of a modifiable exposure on disease by making use of measured Inheritance of quantitative traits or polygenic inheritance refers to the inheritance of a phenotypic characteristic that varies in degree and can be attributed to ^[64] Once a candidate gene is found, further research is often done on the same gene (called an orthologous gene) in model organisms. In Evolutionary biology, homology has come to mean any similarity between characters that is due to their shared ancestry. In addition to studying genetic diseases, the increased availability of genotyping techniques has led to the field of pharmacogenetics—studying how genotype can affect drug responses. The terms Pharmacogenomics and pharmacogenetics tend to be used interchangeably and a precise consensus definition of either remains elusive ^[65]

Although it is not an inherited disease, cancer is also considered a genetic disease. Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled ^[66] The process of cancer development in the body is a combination of events. Mutations occasionally occur within cells in the body as they divide—while these mutations will not be inherited by any offspring, they can affect the behavior of cells, sometimes causing them to grow and divide more frequently. In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism There are biological mechanisms that attempt to stop this process—signals are given to inappropriately dividing cells that should trigger cell death, but sometimes additional mutations occur that cause cells to ignore these messages. An internal process of natural selection occurs within the body and eventually mutations accumulate within cells to promote their own growth, creating a cancerous tumor that grows and invades various tissues of the body. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of

E coli colonies on a plate of agar, an example of cellular cloning and often used in molecular cloning

Research techniques

DNA can be manipulated in the laboratory. In Biology, a colony (from Latin colonia) refers to several individual Organisms of the same Species living closely together usually Agar or agar agar is a Gelatinous substance derived from Seaweed. Cloning in Biology is the process of producing populations of genetically-identical individuals that occurs in nature when organisms such as Bacteria, Insects Molecular cloning refers to the procedure of isolating a defined DNA sequence and obtaining multiple copies of it In vivo. Restriction enzymes are a commonly used enzyme that cuts DNA at specific sequences, producing predictable fragments of DNA. A restriction enzyme (or restriction Endonuclease) is an Enzyme that cuts double-stranded DNA at specific recognition Nucleotide Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins ^[67] The use of ligation enzymes allows these fragments to be reconnected, and by ligating fragments of DNA together from different sources, researchers can create recombinant DNA. In Molecular biology, DNA ligase is a special type of Ligase ( that can link together two DNA strands that have single-strand breaks (a break in both complementary Recombinant DNA is a form of synthetic DNA that is engineered through the combination or insertion of one or more DNA strands thereby combining DNA sequences Often associated with genetically modified organisms, recombinant DNA is commonly used in the context of plasmids—short circular DNA fragments with a few genes on them. This article is about organisms which have been genetically modified A plasmid is an extra-chromosomal DNA molecule separate from the chromosomal DNA which is capable of replicating independently of the chromosomal DNA By inserting plasmids into bacteria and growing those bacteria on plates of agar (to isolate clones of bacteria cells), researchers can clonally amplify the inserted fragment of DNA (a process known as molecular cloning). Cloning in Biology is the process of producing populations of genetically-identical individuals that occurs in nature when organisms such as Bacteria, Insects Cloning in Biology is the process of producing populations of genetically-identical individuals that occurs in nature when organisms such as Bacteria, Insects (Cloning can also refer to the creation of clonal organisms, through various techniques. Cloning in Biology is the process of producing populations of genetically-identical individuals that occurs in nature when organisms such as Bacteria, Insects )

DNA can also be amplified using a procedure called the polymerase chain reaction (PCR). ^[68] By using specific short sequences of DNA, PCR can isolate and exponentially amplify a targeted region of DNA. Because it can amplify from extremely small amounts of DNA, PCR is also often used to detect the presence of specific DNA sequences.

DNA sequencing and genomics

One of the most fundamental technologies developed to study genetics, DNA sequencing allows researchers to determine the sequence of nucleotides in DNA fragments. The term DNA sequencing encompasses biochemical methods for determining the order of the Nucleotide bases Adenine, Guanine, Cytosine Developed in 1977 by Frederick Sanger and coworkers, chain-termination sequencing is now routinely used to sequence DNA fragments. Frederick Sanger, OM, CH, CBE, FRS (born 13 August 1918) is an English biochemist and twice ^[69] With this technology, researchers have been able to study the molecular sequences associated with many human diseases. As sequencing has become less expensive and with the aid of computational tools, researchers have sequenced the genomes of many organisms by stitching together the sequences of many different fragments (a process called genome assembly). Genome projects are Scientific endeavours that ultimately aim to determine the complete Genome sequence of an Organism (be it an Animal, a Genome projects are Scientific endeavours that ultimately aim to determine the complete Genome sequence of an Organism (be it an Animal, a ^[70] These technologies were used to sequence the human genome, leading to the completion of the Human Genome Project in 2003. The Human Genome Project (HGP was an international Scientific research project with a primary goal to determine the sequence of chemical base pairs which make up DNA ^[19]

The large amount of sequences available has created the field of genomics, research that uses computational tools to search for and analyze patterns in the full genomes of organisms. Genomics is the study of an organism's entire Genome. The field includes intensive efforts to determine the entire DNA sequence of organisms and fine-scale Genetic Genomics can also be considered a subfield of bioinformatics, which uses computational approaches to analyze large sets of biological data. Bioinformatics is the application of information technology to the field of molecular biology

References

• Alberts B, Johnson A, Lewis J, Raff M, Roberts K, and Walter P (2002). Molecular Biology of the Cell, 4th edition. ISBN 0-8153-3218-1.  
• Griffiths AJF, Miller JH, Suzuki DT, Lewontin RC, and Gelbart WM (2000). An Introduction to Genetic Analysis. New York: W. H. Freeman and Company. ISBN 0-7167-3520-2.  
• Hartl D, Jones E (2005). Genetics: Analysis of Genes and Genomes, 6th edition. Jones & Bartlett. ISBN 0-7637-1511-5.  
• Lodish H, Berk A, Zipursky LS, Matsudaira P, Baltimore D, and Darnell J (2000). Molecular Cell Biology, 4th edition. ISBN 0-7167-3136-3.  

Notes

External links

• Genetics at the Open Directory Project