Cytogenetics is a branch of genetics that is concerned with the study of chromosomes and cell division. Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is It includes routine analysis of G-Banded chromosomes, other cytogenetic banding techniques, as well as molecular cytogenetics such as fluorescent in situ hybridization (FISH) and comparative genomic hybridization (CGH). G-banding is technique used in Cytogenetics to produce differently stained regions on condensed Chromosomes The Metaphase chromosomes are treated with Molecular cytogenetics involves the combination of Molecular biology and Cytogenetics. FISH ( Fluorescent In situ hybridization) is a cytogenetic technique that can be used to detect and localize the presence or absence Comparative genomic hybridization ( CGH) or Chromosomal Microarray Analysis ( CMA) is a molecular- Cytogenetic method for the analysis of
Chromosomes were first observed in plant cells by Karl Wilhelm von Nägeli in 1842. Karl Wilhelm von Nägeli ( March 27, 1817 – May 11, 1891) was a Swiss botanist. Their behavior in animal (salamander) cells was described by Walther Flemming, the discoverer of mitosis, in 1882. Salamander (orig from Persian: sām, "fire" and andarūn, "within" is the common name for a group of approximately 500 Species Walther Flemming ( April 21[[ 843]] - August 4[[ 905]] was a German Biologist and the founder of Cytogenetics. Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei The name was coined by another German anatomist, von Waldeyer in 1888. Heinrich Wilhelm Gottfried von Waldeyer-Hartz ( October 6, 1836, Hehlen an der Weser, Braunschweig, Germany – January 23
The next stage took place after the development of genetics in the early 20th century, when it was appreciated that the set of chromosomes (the karyotype) was the carrier in the genes. A chromosome is an organized structure of DNA and Protein that is found in cells. A karyotype is the characteristic Chromosome complement of a Eukaryote Species. Levitsky seems to have been the first to define the karyotype as the phenotypic appearance of the somatic chromosomes, in contrast to their genic contents. A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties "Somatic" redirects here for the musician known as Somatic see Hahn Rowe. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance  Investigation into the human karyotype took many years to settle the most basic question: how many chromosomes does a normal diploid human cell contain?  In 1912, Hans von Winiwarter reported 47 chromosomes in spermatogonia and 48 in oogonia, concluding an XX/XO sex determination mechanism. "Haplo" redirects here For the fictional character see The Death Gate Cycle. A spermatogonium (plural spermatogonia) is an intermediary male Gametogonium (a kind of Germ cell) in the production of Spermatozoa. An oogonium (plural oogonia) is an Immature ovum. It is a female Gametogonium. The X0 sex-determination system is a system that Grasshoppers, Crickets, Cockroaches, and some other Insects use to determine the sex of their A sex-determination system is a biological system that determines the development of sexual characteristics in an Organism.  Painter in 1922 was not certain whether the diploid number of man was 46 or 48, at first favouring 46. Theophilus Shickel Painter ( August 22, 1889 &ndash October 5, 1969) was an American zoologist known for his work in identifying  He revised his opinion later from 46 to 48, and he correctly insisted on man having an XX/XY system. The XY sex-determination system is the Sex-determination system found in Humans most other Mammals some insects ( Drosophila) and some  Considering their techniques, these results were quite remarkable.
New techniques were needed to definitively solve the problem:
Barbara McClintock began her career as a maize cytogeneticist. Barbara McClintock (June 16 1902 – September 2 1992 the 1983 Nobel Laureate in Physiology or Medicine, was an American scientist and one of the world's most distinguished Maize (ˈmeɪz ( Zea mays L. ssp mays) known as corn in some countries is a cereal grain domesticated in Mesoamerica In 1931 McClintock and Harriet Creighton demonstrated that cytological recombination of marked chromosomes correlated with recombination of genetic traits (genes). Year 1931 ( MCMXXXI) was a Common year starting on Thursday (link will display full 1931 calendar of the Gregorian calendar. Harriet Baldwin Creighton ( 27 June 1909 &ndash January 9 2004) was an American Botanist, Geneticist and educator A chromosome is an organized structure of DNA and Protein that is found in cells. A trait is a distinct phenotypic character of an organism that may be inherited environmentally determined or somewhere in between History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance McClintock continued her career in cytogenetics studying the mechanics and inheritance of broken and ring (circular) chromosomes of maize. During her cytogenetic work, McClintock discovered transposons, a find which eventually led to her Nobel Prize in 1983. Transposons are sequences of DNA that can move around to different positions within the Genome of a single cell, a process called transposition The Nobel Prize (Nobelpriset (Nobelprisen is a Swedish prize established in the 1895 will of Swedish chemist Alfred Nobel; it was first awarded in Peace, Literature Year 1983 ( MCMLXXXIII) was a Common year starting on Saturday (link displays the 1983 Gregorian calendar)
In the 1930s Dobzhansky and his co-workers collected Drosophila pseudoobscura and D. Theodosius Grygorovych Dobzhansky, also known Drosophila pseudoobscura is a Species of fruit fly, used extensively in lab studies of Speciation. persimilis from wild populations in California and neighbouring states. California ( is a US state on the West Coast of the United States, along the Pacific Ocean. Using Painter's technique  they studied the polytene chromosomes and discovered that the wild populations were polymorphic for chromosomal inversions. To increase cell volume some specialized cells undergo repeated rounds of DNA replication without Cell division ( endomitosis) forming a giant polytene An inversion is a Chromosome rearrangement in which a segment of a chromosome is reversed end to end All the flies look alike whatever inversions they carry: this is an example of a cryptic polymorphism.
Evidence rapidly accumulated to show that natural selection was responsible. Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of Using a method invented by L'Heretier and Teissier, Dobzhansky bred populations in population cages, which enabled feeding, breeding and sampling whilst preventing escape. This had the benefit of eliminating migration as a possible explanation of the results. Insect migration is the seasonal movement of Insects particularly those by species of dragonflies, Beetles butterflies and Moths Stocks containing inversions at a known initial frequency can be maintained in controlled conditions. It was found that the various chromosome types do not fluctuate at random, as they would if selectively neutral, but adjust to certain frequencies at which they become stabilised. By the time Dobzhansky published the third edition of his book in 1951 he was persuaded that the chromosome morphs were being maintained in the population by the selective advantage of the heterozygotes, as with most polymorphisms. Polymorphism in biology occurs when two or more clearly different Phenotypes exist in the same population of a species — in other words the occurrence of more than one 
With the advent of procedures which allowed easy enumeration of chromosomes, discoveries were quickly made in abnormalities arising from nondysjunction events which cause cells with aneuploidy (additions or deletions of entire chromosomes). Aneuploidy is defined as an abnormal number of Chromosomes Syndromes caused by an extra or missing chromosome are among the most widely recognized Genetic disorders In 1959 Lejeune discovered patients with Down syndrome had an extra copy of chromosome 21. The year 1959 ( MCMLIX) was a Common year starting on Thursday (link will display full calendar of the Gregorian calendar. Down syndrome, Down's syndrome, or trisomy 21 is a Chromosomal disorder caused by the presence of all or part of an extra 21st chromosome. Down syndrome is also referred to as trisomy 21. In 1960 Nowell discovered a small chromosome, dubbed the Philadelphia chromosome, which was shown to be the cause of Chronic myelogenous leukemia. Year 1960 ( MCMLX) was a Leap year starting on Friday (link will display full calendar of the Gregorian calendar. Philadelphia chromosome or Philadelphia translocation is a specific chromosomal abnormality that is associated with Chronic myelogenous leukemia (CML Chronic myelogenous (or myeloid leukemia ( CML) is a form of Leukemia characterized by the increased and unregulated growth of predominantly Myeloid cells 13 years later this was shown by Janet Rowley to be a translocation of chromosomes 9 and 22. Janet Davison Rowley (born 1925 is an American human Geneticist and the first scientist to identify a Chromosomal translocation as the cause of Leukemia
Other numerical abnormalities discovered include sex chromosome abnormalities. An individual with only one sex chromosome (the X) has Turner syndrome, an additional X chromosome in a male, resulting in 47 total chromosomes, has Klinefelter's Syndrome. Turner syndrome or Ullrich-Turner syndrome encompasses several conditions of which monosomy X is the most common Klinefelter's syndrome, 47XXY or XXY syndrome is a condition caused by a Chromosome Aneuploidy. Many other sex chromosome combinations are compatible with live birth including XXX, XYY, and XXXX. The ability for mammals to tolerate aneuploidies in the sex chromosomes arises from the ability to inactivate them, which is required in normal females to compensate for having two copies of the chromosome. In those species (including humans in which sex is determined by the presence of the Y or X Chromosome rather than the diploidy of the X or Z a Barr body is Not all genes on the X Chromosome are inactivated, which is why there is a phenotypic effect seen in individuals with an extra or missing X.
Trisomy 13 was associated with Patau's Syndrome and trisomy 18 with Edward's Syndrome. Patau syndrome, also known as trisomy 13, is a chromosomal abnormality a Syndrome in which a patient has an additional chromosome 13 due Trisomy 18 or Edwards Syndrome is a Genetic disorder caused by the presence of all or part of an extra 18th chromosome.
In the late 1960s Caspersson developed banding techniques which differentially stain chromosomes. Professor Torbjörn Oskar Caspersson ( October 15, 1910 &ndash December 7, 1997) was a Swedish cytologist and geneticist This allows chromosomes of otherwise equal size to be differentiated as well as to elucidate the breakpoints and constituent chromosomes involved in chromosome translocations. In Genetics, a chromosome translocation is a Chromosome abnormality caused by rearrangement of parts between nonhomologous Chromosomes. Deletions within one chromosome could also now be more specifically named and understood. Deletion syndromes such as DiGeorge syndrome, Prader-Willi syndrome and others were discovered to be caused by deletions in chromosome material. 22q112 deletion syndrome, also known as Velocardiofacial Syndrome DiGeorge Syndrome conotruncal anomaly face syndrome Congenital Thymic Aplasia and Strong Syndrome is a disorder caused Prader-Willi syndrome (abbreviated PWS) is a very rare Genetic disorder, in which seven genes (or some subset thereof on chromosome 15 are missing or unexpressed
Diagrams identifying the chromosomes based on the banding patterns are known as cytogenetic maps. These maps became the basis for both prenatal and oncological fields to quickly move cytogenetics into the clinical lab where karyotyping allowed scientists to look for chromosomal alterations. Techniques were expanded to allow for culture of free amniocytes recovered from amniotic fluid, and elongation techniques for all culture types that allow for higher resolution banding.
In the 1980s advances were made in molecular cytogenetics. The 1980s was the decade spanning from January 1 1980 to December 31 1989. Molecular cytogenetics involves the combination of Molecular biology and Cytogenetics. While radioisotope-labeled probes had been hybridized with DNA since 1969, movement was now made in using fluorescently labeled probes. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Year 1969 ( MCMLXIX) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar. Hybridizing them to chromosomes preparations made using existing techniques came to be known as fluorescent in situ hybridization (FISH). FISH ( Fluorescent In situ hybridization) is a cytogenetic technique that can be used to detect and localize the presence or absence This change significantly increased the usage of probing techniques as fluorescently labeled probes are safer and can be used almost indefinitely. Further advances in micromanipulation and examination of chromosomes led to the technique of chromosome microdissection whereby aberrations in chromosomal structure could be isolated, cloned and studied in ever greater detail. Chromosome microdissection is a technique that physically removes a large section of DNA from a complete Chromosome.
In some forms of cancer, especially hematological malignancies, cytogenetics can determine which chromosomal translocations are present in the malignant cells, facilitating diagnosis and susceptibility to treatment (e. Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled Hematological malignancies are the types of Cancer that affect Blood, Bone marrow, and Lymph nodes As the three are intimately connected through In Genetics, a chromosome translocation is a Chromosome abnormality caused by rearrangement of parts between nonhomologous Chromosomes. g. imatinib mesylate in the presence of the Philadelphia chromosome). Imatinib is a drug used to treat certain types of Cancer. It is currently marketed by Novartis as Gleevec ( USA) or Glivec Philadelphia chromosome or Philadelphia translocation is a specific chromosomal abnormality that is associated with Chronic myelogenous leukemia (CML
In congenital disorders, such as Down's syndrome, cytogenetics can determine the nature of the chromosomal defect - a "simple" trisomy, a mosaic, "balanced" translocation, a deletion, or an insertion in one - or both - of the parents, or in the fetus. Down syndrome, Down's syndrome, or trisomy 21 is a Chromosomal disorder caused by the presence of all or part of an extra 21st chromosome. In Medicine ( Genetics) a mosaic or mosaicism denotes the presence of two populations of cells with different Genotypes in one In Genetics, a chromosome translocation is a Chromosome abnormality caused by rearrangement of parts between nonhomologous Chromosomes. With the advent of harvest procedures which allowed easy enumeration of chromosomes, discoveries were quickly made in abnormalities arising from nondysjunction events which cause cells with aneusomy (additions or deletions of entire chromosomes). In 1959 Lejeune discovered patients with Down syndrome had an extra copy of chromosome 21. Down syndrome is also referred to as trisomy 21. In 1960 Nowell discovered a small chromosome, dubbed the Philadelphia chromosome, which was shown to be the cause of Chronic myelogenous leukemia. 13 years later this was shown by Janet Rowley to be a translocation of chromosomes 9 and 22.
Other numerical abnormalities discovered include sex chromosome abnormalities. An individual with only one sex chromosome (the X) has Turner syndrome, an additional X chromosome in a male, resulting in 47 total chromosomes, has Klinefelter's Syndrome. Many other sex chromosome combinations are compatible with live birth including XXX, XYY, and XXXX. The ability for mammals to tolerate aneusomies in the sex chromosomes arises from the ability to inactivate them, which is required in normal females to compensate for having two copies of the chromosome.
Trisomy 13 was associated with Patau's Syndrome and trisomy 18 with Edward's Syndrome.
Routine chromosome analysis refers to analysis of metaphase chromosomes which have been banded using trypsin followed by Giemsa, Leishmanns, or a mixture of the two. Metaphase from the Ancient Greek μετά (after and φάσις (stage is a stage of Mitosis in the eukaryotic Cell cycle in which A chromosome is an organized structure of DNA and Protein that is found in cells. Trypsin ( is a Serine protease found in the Digestive system, where it breaks down Proteins Trypsin predominantly cleaves peptide chains at the carboxyl Giemsa stain, named after Gustav Giemsa, an early malariologist is used for the histopathological diagnosis of Malaria and other Parasites It is a mixture This creates unique banding patterns on the chromosomes. The molecular mechanism and reason for these patterns is unknown, although it likely related to replication timing and chromatin packing.
Several chromosome-banding techniques are used in cytogenetics laboratories. Quinacrine banding (Q-banding) was the first staining method used to produce specific banding patterns. Quinacrine (trade name Atabrine) is a drug with a number of different medical applications being initially used in the 1930s as an Antimalarial drug This method requires a fluorescence microscope and is no longer as widely used as Giemsa banding (G-banding). Giemsa stain, named after Gustav Giemsa, an early malariologist is used for the histopathological diagnosis of Malaria and other Parasites It is a mixture Reverse banding (R-banding) requires heat treatment and reverses the usual white and black pattern that is seen in G-bands and Q-bands. This method is particularly helpful for staining the distal ends of chromosomes. Other staining techniques include C-banding and nucleolar organizing region stains (NOR stains). These latter methods specifically stain certain portions of the chromosome. C-banding stains the constitutive heterochromatin, which usually lies near the centromere, and NOR staining highlights the satellites and stalks of acrocentric chromosomes. Heterochromatin is a tightly packed form of DNA Its major characteristic is that transcription is limited A centromere is a region of DNA typically found near the middle of a Chromosome where two Sister chromatids come in contact High-resolution banding involves the staining of chromosomes during prophase or early metaphase (prometaphase), before they reach maximal condensation. Prophase is a stage of Mitosis in which the Chromatin condenses into a highly ordered structure called a Chromosome Metaphase from the Ancient Greek μετά (after and φάσις (stage is a stage of Mitosis in the eukaryotic Cell cycle in which Because prophase and prometaphase chromosomes are more extended than metaphase chromosomes, the number of bands observable for all chromosomes increases from about 300 to 450 to as many as 800. Prophase is a stage of Mitosis in which the Chromatin condenses into a highly ordered structure called a Chromosome Prometaphase is the phase of Mitosis following Prophase and preceding Metaphase, in eukaryotic Somatic cells The nuclear This allows the detection of less obvious abnormalities usually not seen with conventional banding.
Cells from bone marrow, blood, amniotic fluid, cord blood, tumor, and tissues (including skin, umbilical cord, liver, and many other organs) can be cultured using standard cell culture techniques in order to increase their number. Umbilical cord blood up to 180mL of Blood from a newborn baby that is returned to the neonatal circulation if the Umbilical cord is not prematurely clamped A mitotic inhibitor (colchicine, colcemid) is then added to the culture. A mitotic inhibitor is a type of drug derived from natural substances such as plant Alkaloids and primarily used in cancer treatment and certain types of cancer research including This stops cell division at mitosis which allows an increased yield of mitotic cells for analysis. Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei The cells are then centrifuged and media and mitotic inhibitor is removed, and replaced with a hypotonic solution. This causes the cells to swell so that the chromosomes will spread when added to a slide. After the cells have been allowed to sit in hypotonic, Carnoy's fixative (3:1 methanol to glacial acetic acid) is added. Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a Chemical compound Acetic acid, also known as ethanoic acid, is an organic chemical compound, giving Vinegar its sour taste This kills the cells, lyses the red blood cells, and hardens the nuclei of the remaining white blood cells. The cells are generally fixed repeatedly to remove any debris or remaining red blood cells. The cell suspension is then dropped onto specimen slides. After aging the slides in an oven or waiting a few days they are ready for banding and analysis.
Analysis of banded chromosomes is done at a microscope by a clinical laboratory specialist in cytogenetics (CLSp(CG)). A microscope ( Greek: ( micron) = small + ( skopein) = to look or see is an instrument for viewing objects that are Generally 20 cells are analyzed which is enough to rule out mosaicism to an acceptable level. The results are summarized and given to a board-certified medical geneticist and a pathologist for review, and to write an interpretation taking into account the patients previous history and other clinical findings. Pathology (from Greek grc πάθος pathos, "fate harm" and grc -λογία -logia) is the study and The results are then given out reported in an International System for Human Cytogenetic Nomenclature 2005 (ISCN2005).
Fluorescent in situ hybridization refers to using fluorescently labeled probe to hybridize to cytogenetic cell preparations. FISH ( Fluorescent In situ hybridization) is a cytogenetic technique that can be used to detect and localize the presence or absence FISH ( Fluorescent In situ hybridization) is a cytogenetic technique that can be used to detect and localize the presence or absence
In addition to standard preparations FISH can also be performed on:
This section refers to preparation of standard cytogenetic preparations
The slide is aged using a salt solution usually consisting of 2X SSC (salt, sodium citrate). The slides are then dehydrated in ethanol, and the probe mixture is added. The sample DNA and the probe DNA are then co-denatured using a heated plate and allowed to re-anneal for at least 4 hours. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known The slides are then washed to remove excess unbound probe, and counterstained with 4',6-Diamidino-2-phenylindole (DAPI) or propidium iodide. DAPI or 4'6-diamidino-2-phenylindole is a fluorescent stain that binds strongly to DNA.
Analysis of FISH specimens is done by fluorescence microscopy by a clinical laboratory specialist in cytogenetics (CLSp(CG)). A fluorescence microscope (colloquially synonymous with epifluorescent microscope) is a light Microscope used to study properties of organic or inorganic substances For oncology generally a large number of interphase cells are scored in order to rule out low level residual disease, generally between 200 and 1000 cells are counted and scored. Interphase is the phase of the Cell cycle in which the cell spends the majority of its time and performs the majority of its purposes including preparation for Cell For congenital problems usually 20 metaphase cells are scored.
Advances now focus on molecular cytogenetics including techniques such as comparative genomic hybridization arrays, CGH, SNP-array based karyotyping and automated systems for counting the results of standard FISH preparations. Molecular cytogenetics involves the combination of Molecular biology and Cytogenetics.