Human genetics describes the study of inheritance as it occurs in human beings. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Human genetics encompasses a variety of overlapping fields including: classical genetics, cytogenetics, molecular genetics, biochemical genetics, genomics, population genetics, developmental genetics, clinical genetics, and genetic counseling. Classical genetics consists of the techniques and methodologies of Genetics that predate the advent of Molecular biology. Cytogenetics is a branch of Genetics that is concerned with the study of chromosomes and cell division Molecular genetics is the field of Biology which studies the structure and function of Genes at a molecular level Molecular biology is the study of Biology at a molecular level 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 Population genetics is the study of the Allele frequency distribution and change under the influence of the four evolutionary forces Natural selection, Genetic Developmental Biology is the official journal of the Society for Developmental Biology. Medical genetics is the specialty of Medicine that involves the diagnosis and management of Hereditary disorders Medical genetics differs from Human genetics Genetic counseling is the process by which patients or relatives at risk of an inherited disorder are advised of the consequences and nature of the disorder the probability of developing Study of human genetics can be useful as it can answer questions about human nature, understand the diseases and development of effective disease treatment, and understand genetics of human life. This article describes only basic features of human genetics; for the genetics of disorders please see: Medical genetics. Medical genetics is the specialty of Medicine that involves the diagnosis and management of Hereditary disorders Medical genetics differs from Human genetics

Contents 1 Genetic Differences and Inheritance Patterns 1.1 Autosomal Dominant Inheritance 1.2 Autosomal Recessive Inheritance 1.3 X-Linked and Y-Linked Inheritance 1.4 Pedigrees 1.5 Karyotype 2 Genomics 3 Population Genetics 3.1 Hardy-Weinberg Principle 4 Mitochondrial DNA 5 Genes and human characteristics 5.1 Genes and behavior 5.2 Genes and gender 5.3 Genes 5.4 Evolutionary psychology 5.5 Genetic disorders 5.6 Human traits with simple inheritance patterns 6 See also 7 References 8 External links

Genetic Differences and Inheritance Patterns

Inheritance of traits for humans are based upon Gregor Mendel's model of inheritance. Gregor Johann Mendel ( July 20, 1822 &ndash January 6, 1884) was Mendel deduced that inheritance depends upon discrete units of inheritance, called genes. ^[1]

Autosomal Dominant Inheritance

Autosomal traits are associated with a single on an autosome (non-sex chromosome)—they are called "dominant" because a single copy—inherited from either parent—is enough to cause this trait to appear. This often means that one of the parents must also have the same trait, unless it has arisen due to a new mutation. Examples of autosomal dominant traits and disorders are Huntington's disease, and achondroplasia. Huntington's disease, also called Huntington's chorea, chorea major, or HD, is a genetic neurological disorder characterized after Achondroplasia is a type of Autosomal dominant Genetic disorder that is a common cause of Dwarfism.

Autosomal Recessive Inheritance

Autosomal recessive traits is one pattern of inheritance for a trait, disease, or disorder to be passed on through families. For a recessive trait or disease to be displayed two copies of the trait or disorder needs to be presented. The trait or gene will be located on a non-sex chromosome. Due to the fact that it takes two copies of a trait to display a trait, many people can unknowingly be carriers of a disease. from an evolutionary aspect, a recessive disease or trait can remain hidden for several generations before displaying the phenotype. Examples of autosomal recessive disorders are albinism, Cystic Fibrosis, Tay-Sachs disease

X-Linked and Y-Linked Inheritance

X-linked genes are found on the sex X chromosome. Albinism (from Latin albus, "white" see extended etymology) is a form of hypopigmentary Congenital disorder, Cystic fibrosis (also known as CF, mucoviscoidosis, or mucoviscidosis) is a hereditary disease affecting the exocrine (mucus glands of the lungs Tay-Sachs disease (abbreviated TSD, also known as GM2 Gangliosidosis, Hexosaminidase A deficiency or Sphingolipidosis) is a Genetic X-linked genes just like autosomal genes have both dominant and recessive types. Recessive X-linked disorders are rarely seen in females and usually only affect males. This is because males inherit their X chromosome and all X-linked genes will be inherited from the maternal side. Fathers only pass on their Y chromosome to their sons, so no X-linked traits will be inherited from father to son. Females express X-linked disorders when they are homozygous for the disorder and become carriers when they are heterozygous. An infamous recessive X-linked disorder is Hemophilia A. Haemophilia A (also spelled Hemophilia A or Hæmophilia A) is a Blood clotting disorder caused by a mutation of the Factor VIII gene Hemophilia is a disorder where blood does not clot properly due to a shortage of clotting factor VII. This disorder gained recognition as it traveled through royal families, notably the descendent's of Britain's Queen Victoria. X-linked dominant inheritance will show the same phenotype as a heterozygote and homozygote. Just like X-linked inheritance, there will be a lack of male-to-male inheritance, which makes it distinguishable from autosomal traits. one example of a X-linked trait is Coffin-Lowry syndrome, which is caused by a mutation in ribosomal protein gene. Coffin-lowry syndrome was characterised by Coffin (1966 and Lowry (1971 This mutation results in skeletal, craniofacial abnormalities, mental retardation, and short stature.

X chromosomes in females undergo a process known as X inactivation. X inactivation is when one of the two X chromosomes in females is almost completely inactivated. It is important that this process occurs otherwise a woman would produce twice the amount of normal X chromosome proteins. The mechanism for X inactivation will occur during the embryonic stage. For people with disorders like trisomy X, where the genotype has three X chromosomes, X-inactivation will inactivate all X chromosomes until there is only one X chromosome active. Triple X syndrome is a form of chromosomal variation characterized by the presence of an extra X chromosome in each cell of a human female X inactivation is not only limited to females, males with Klinefelter syndrome, who have an extra X chromosome, will also undergo X inactivation to have only one completely active X chromosome. Klinefelter's syndrome, 47XXY or XXY syndrome is a condition caused by a Chromosome Aneuploidy.

Y-linked inheritance occurs when a gene, trait, or disorder is transferred through the Y chromosome. Since Y chromosomes can only be found in males, Y linked traits are only passed on from father to son. The testis determining factor, which is located on the Y chromosome, determines the maleness of individuals. Testis-determining factor ( TDF) is a general term for the Gene (or product thereof that results in Maleness in humans and some other species Besides the maleness inherited in the Y-chromosome there are no other found Y-linked characteristics.

Pedigrees

A pedigree is a diagram showing the ancestral relationships and transmission of genetic traits over several generations in a family. Pedigrees are used to help detect many different genetic diseases. A pedigree can also be used to help determine the chances for a parent to produce an offspring with a specific trait. Four different traits can be identified by pedigree chart analysis: autosomal dominant, autosomal recessive, x-linked, or y-linked. Partial penetrance can be shown and calculated form pedigrees. Penetrance is the percentage expressed frequency with which individuals of a given genotype manifest at least some degree of a specific mutant phenotype associated with a trait. Inbreeding, the mating between closely related organisms of traits can clearly been seen on pedigree charts. Inbreeding is breeding between close Relatives whether plant or animal Pedigree charts of royal families have a high degree of inbreeding, because it was customary and prefferable for royalty to marry another member of royalty. Genetic councilors commonly use pedigrees to help couple determine if the parents will be able to produce healthy children.

Karyotype

A karyotype is a very useful tool in cytogenetics. A karyotype is the characteristic Chromosome complement of a Eukaryote Species. A karyotype is picture of all the chromosomes in the metaphase stage arranged according to length and centromere position. Metaphase from the Ancient Greek μετά (after and φάσις (stage is a stage of Mitosis in the eukaryotic Cell cycle in which A karyotype can also be useful in clinical genetics, due to its ability to diagnose genetic disorders. On a normal karyotype, aneuploidy can be detected by clearly being able to observe any missing or extra chromosomes. Giemsa banding, g-banding, of the karyotype can be used to detect deletions, insertions, duplications, inversions, and translocations. G-banding is technique used in Cytogenetics to produce differently stained regions on condensed Chromosomes The Metaphase chromosomes are treated with In Genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) is a Mutation (a genetic aberration Genetic Insertion is the addition of one or more Nucleotide Base pairs into a genetic sequence In Genetics, a chromosome translocation is a Chromosome abnormality caused by rearrangement of parts between nonhomologous Chromosomes. G-banding will stain the chromosomes with light and dark bands unique to each chromosome. A FISH, fluorescent in situ hybridization, can be used to observe deletions, insertions, and translocations. FISH ( Fluorescent In situ hybridization) is a cytogenetic technique that can be used to detect and localize the presence or absence FISH uses fluorescent probes to bind to specific sequences of the chromosomes that will cause the chromosomes to fluoresce a unique color. ^[2]

Genomics

Genomics refers to the field of genetics concerned with structural and functional studies of the genome. ^[3] A genome is all the DNA contained within an organism or a cell including nuclear and mitochondrial DNA. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby The human genome is the total collection of genes in a human being contained in the human chromosome, composed of over three billion nucleotides. The human genome is the Genome of Homo sapiens, which is stored on 23 chromosome pairs ^[4] In April 2003, the Human Genome Project was able to sequence all the DNA in the human genome, to discover the human genome was composed around 20,000 protein coding genes. 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

Population Genetics

Population genetics is the branch of evolutionary biology responsible for investigating processes that cause changes in allele and genotype frequencies in populations based upon Mendelian inheritance. Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent ^[5] Four different forces can influence the frequencies: natural selection, mutation, gene flow(migration), and genetic drift. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism In Population genetics, gene flow (also known as gene migration) is the transfer of Alleles of Genes from one Population to another 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 A population can be defined as a group of interbreeding individuals and their offspring. For human genetics the populations will consist only of the human species. The Hardy-Weinberg principle is a widely used principle to determine allelic and genotype frequencies.

Hardy-Weinberg Principle

Hardy-Weinberg principle states that when no evolution occurs in a population the allele and genotype frequencies do not change from one generation to the next. No evolution refers to no mutation, no gene flow, no natural selection, and no genetic drift. To be in equilibrium two more assumptions need to be made that random mating occurs and there are discrete, non-overlapping generations.

Mitochondrial DNA

In addition to nuclear DNA, humans (like almost all eukaryotes) have mitochondrial DNA. Nuclear DNA, nuclear deoxyribonucleic acid (nDNA is DNA contained within a nucleus of eukaryotic organisms. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Mitochondrial DNA ( mtDNA) is the DNA located in Organelles called mitochondria. Mitochondria, the "power houses" of a cell, have their own DNA because they are descended from a proteobacterium that merged with eukaryotic cells over 2 billion years ago; an assertion known as the endosymbiotic hypothesis. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. The Proteobacteria are a major group ( Phylum) of Bacteria. They include a wide variety of Pathogens such as Escherichia, The endosymbiotic theory concerns the origins of mitochondria and Plastids (e Mitochondria are inherited from one's mother, and its DNA is frequently used to trace maternal lines of descent (see mitochondrial Eve). Mitochondrial Eve ( mt-mrca) is the name given by researchers to the woman who is defined as the Matrilineal most recent common ancestor (MRCA for all currently Mitochondrial DNA is only 16kb in length and encodes for 37 genes.

Genes and human characteristics

Genes are the fundamental units of inheritance. Genes can be defined as a sequence of DNA in the genome that is required for production of a functional product. Genes have both minor and major effects on human characteristics. Human genes have become prominent in the nature versus nurture debate. The nature versus nurture debates concern the relative importance of an individual's innate qualities ("nature" i

Genes and behavior

Genes have a strong influence on human behavior. IQ is largely heritable. An Intelligence Quotient or IQ is a score derived from one of several different Standardized tests attempting to measure Intelligence. Study of the heritability of IQ is a controversial field of research that includes biology psychology philosophy sociology and anthropology However, this has been questioned. The stance that humans inherit substantial behavioral characteristics is called psychological nativism, compared to the stance that human behavior and culture are virtually entirely constructed (tabula rasa). For nativism as a political force see Nativism. In the field of Psychology, nativism is the view that certain skills or abilities Tabula rasa ( Latin: blank slate) refers to the epistemological thesis that individual human beings are born with no built-in mental content

In the early 20th century, eugenics was policy in parts of the United States and Europe. Eugenics is a social Philosophy which advocates the improvement of Human Hereditary traits through various forms of intervention The goal was to reduce or eliminate traits that were considered undesirable. One form of eugenics was compulsory sterilization of people deemed mentally unfit. Compulsory sterilization programs are government policies which attempt to force people to undergo surgical sterilization. Hitler's eugenics programs turned social consciousness against the practice, and psychological nativism became associated with racism and sexism. Hi and welcome to Wikipedia! Please understand that this article is frequently vandalized and vandalism is reverted immediately Social consciousness is consciousness shared within a Society.

Genes and gender

The biggest genetic difference among healthy humans is in gender. Scientists debate the extent to which genes and culture affect gender roles. The case of David Reimer was once a case in point for the tabula rasa camp, though recently that same case has become evidence for a strong genetic component to gender identity. David Reimer ( August 22, 1965 as Bruce Reimer – May 4, 2004) was a Canadian man who was born as a healthy boy but was sexually

Genes

Most genetic diversity occurs within races rather than between them. The Radio Amateur Civil Emergency Service (RACES is a standby radio service provided for in Part 97 Common concepts of racial categories do not accurately match genetic characteristics.

Evolutionary psychology

Evolutionary psychology explains many human behaviors as more or less moderated by genes that evolved in the hunter-gatherer stage of human cultural development. Evolutionary psychology ( EP) attempts to explain mental and psychological traits ��such as Memory, Perception, See for example Stockholm syndrome. Stockholm syndrome is a psychological response sometimes seen in an abducted hostage in which the hostage shows signs of loyalty to the hostage-taker regardless of the danger

Genetic disorders

Main article: Genetic disorder

Humans have several genetic diseases, often caused by recessive genes. A genetic disorder is a condition caused by abnormalities in Genes or Chromosomes While some diseases such as Cancer, are due to genetic abnormalities acquired A genetic disorder is a condition caused by abnormalities in Genes or Chromosomes While some diseases such as Cancer, are due to genetic abnormalities acquired A few examples of human genetic diseases are: Turner Syndrome, Huntington's disease, cancer, autism, and sickle cell anemia. For a more comprehensive list see List of genetic disorders. The following is a list of Genetic disorders and if known causal type of Mutation and the Chromosome involved Genetic disorders happen everywhere and are very common in some places.

• Cri du Chat syndrome- A disorder caused from a deletion on the short arm of chromosome 5. Cri du Chat syndrome or Cri-du-Chat syndrome (French for Cry or call of the cat referring to the specific cry of the child also called This deletion results in a phenotype of mental retardation, behavioral problems, and a cat like call. A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties About one in every 50,000 births will have the syndrome. ^[6]
• Huntington's disease- A neurological disorder caused by a trinucleotide repeat sequence. Huntington's disease, also called Huntington's chorea, chorea major, or HD, is a genetic neurological disorder characterized after Huntingtons is an autosomal dominant trait. Most individuals with the disease will first display the phenotype around 40 years of age. The symptoms are jerky uncontrollable movements, mental retardation, and behavioral problems. ^[7]
• Turner syndrome- A condition that effects females caused by a 45, XO genotype instead of the normal XX genotype. Turner syndrome or Ullrich-Turner syndrome encompasses several conditions of which monosomy X is the most common These individuals have only one X chromosome. These individuals are phenotypically female, but will be sterile due to undeveloped ovaries. ^[8]
• Klinefelter syndrome- A disorder in males caused by the presence of an extra X chromosome. Klinefelter's syndrome, 47XXY or XXY syndrome is a condition caused by a Chromosome Aneuploidy. These individuals have a genotype of 47, XXY instead of the normal XY genotype. The symptoms for this syndrome are enlarged breasts, small testes, and sterility. ^[9]

Human traits with simple inheritance patterns

Dominant	Recessive	References
Widow's peak	No Widow's peak	[10][11]
Facial Dimples	No Facial Dimples	[12][13]
Able to taste PTC	Unable to taste PTC	[14]
Unattached earlobe	Attached earlobe	[12][15][16]
Cleft chin	No Cleft chin	[17]
Brunette iris	Blue Iris
Color Vision	Color Blind
Freckles	No Freckles	[12][18]
Wet-type earwax	Dry-type earwax	[15][19]

See also

• Human evolutionary genetics
• Human genome
• Genetic genealogy
• Genealogical DNA test
• List of Mendelian traits in humans

References

External links

• Human Genome Project
• How many Genes do humans have?
• Human Genetics Video

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