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Encyclopedia > Cytogenetics
A metaphase cell positive for the bcr/abl rearrangement using FISH
A metaphase cell positive for the bcr/abl rearrangement using FISH

Cytogenetics is the study of the structure of chromosome material. 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). FISH image of bcr/abl positive rearranged metaphase File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... FISH image of bcr/abl positive rearranged metaphase File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Figure 1: Chromosome. ... FISH (Fluorescent in situ hybridization) is a cytogenetic technique which can be used to detect and localize DNA sequences on chromosomes. ... Comparative genomic hybridization (CGH) is a molecular-cytogenetic method for the analysis of regional changes in the DNA content of tumor cells. ...

Contents


History

Early years

Barbara McClintock began her career as a maize cytogeneticist. In 1931 McClintock and Harriet Creighton demonstrated that cytological recombination of marked chromosomes correlated with recombination of genetic traits (genes). 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. Barbara McClintock Barbara McClintock (June 16, 1902 – September 2, 1992) was a pioneering American scientist and one of the worlds most distinguished cytogeneticists. ... Binomial name Zea mays L. Maize (Zea mays ssp. ... 1931 (MCMXXXI) is a common year starting on Thursday. ... Harriet B. Creighton (d. ... This article is about the biological chromosome. ... In biology, a trait or character is a genetically inherited feature of an organism. ... This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... Transposons are sequences of DNA that can move around to different positions within the genome of a single cell, a process called transposition. ... Sir Edward Appletons medal Photographs of Nobel Prize Medals. ... 1983 (MCMLXXXIII) was a common year starting on Saturday of the Gregorian calendar. ...


Modern cytogenetics is generally said to have begun in 1956 with the discovery that normal human cells contain 46 chromosomes by Tjio and Levan[1]. This discovery was aided by a new technique of slide preparation utilizing a hypotonic solution discovered by TC Hsu in 1952. A hypotonic solution is a salt solution less concentrated than that inside human cells, when added to a cell solution this causes the cells to swell. When the cells are added to the slide after treatment with hypotonic the chromosomes spread much better allowing for much easier enumeration. Previously humans were thought to have 48 chromosomes. 1956 (MCMLVI) was a leap year starting on Sunday of the Gregorian calendar. ... Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu  (extinct) Homo sapiens sapiens Homo (genus). ... This article is about the biological chromosome. ... Professor T. C. Hsu, (17 April 1917 - 9 July 2003), was a cell biologist. ... 1952 (MCMLII) was a Leap year starting on Tuesday (link will take you to calendar). ...


It is notable that while Flemming and Arnold first observed human chromosomes in the 1880s, the number of human chromosomes remained unknown for over 70 years. The causes for this are numerous. For many valid scientific reasons, many geneticists at the time relied heavily on animal models for their research, and thus research in human genetics did not keep up with species like the fruit fly Drosophila. This was also the period of the eugenics movement and many geneticists wanted to distance themselves from human genetics. 1880 (MDCCCLXXX) was a leap year starting on Thursday (see link for calendar). ... Binomial name Drosophila melanogaster Meigen, 1830 Drosophila melanogaster Meigen , 1830 (Black-bellied Dew-lover) a dipteran (two-winged) insect, is the species of fruit fly that is commonly used in genetic experiments; it is among the most important model organisms. ... Eugenics is the self-direction of human evolution: Logo from the Second International Congress of Eugenics, 1921, depicting it as a tree which unites a variety of different fields. ...


Progress in numerical abnormalities

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[2] discovered patients with Down syndrome had an extra copy of chromosome 21. Down syndrome is also referred to as trisomy 21. In 1960 Nowell[3] 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. 1959 (MCMLIX) was a common year starting on Thursday of the Gregorian calendar. ... 1960 (MCMLX) was a leap year starting on Friday (link will take you to calendar). ... Philadelphia chromosome or Philadelphia translocation is a specific genetic, chromosomal abnormality that is associated with chronic myelogenous leukemia (CML) and involves an exchange of material between chromosomes 9 and 22. ... Chronic myelogenous leukemia (or CML) is a form of chronic leukemia characterised by increased production of myeloid cells in the bone marrow. ... Dr Janet Davison Rowley (born 1925) is an American human geneticist, she was the first scientist to identify a chromosomal translocation as the cause of leukemia and other cancers. ...


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. Klinefelters syndrome is a condition caused by a chromosome nondisjunction in males; affected individuals have a pair of X sex chromosomes instead of just one, and is associated with additional risk for some medical conditions. ... In those species in which sex is determined by the presence of the Y or W chromosome rather than the diploidy of the X or Z, a Barr body is the inactive X chromosome in a female cell, or the inactive Z in a male (Lyon, 2003), rendered inactive in...


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 aberration, a disease in which a patient has an additional chromosome 13. ... Trisomy 18 or Edwards Syndrome (named after John H. Edwards) is a genetic disorder. ...


Advent of banding techniques

Human male karyotype
Human male karyotype

In the late 1960's Caspersson developed banding techniques which differentially stain chromosomes. This allows chromosomes of otherwise equal size to be differentiated as well as to elucidate the breakpoints and constituent chromosomes involved in chromosome translocations. 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. Image File history File links NHGRI_human_male_karyotype. ... Image File history File links NHGRI_human_male_karyotype. ... Professor Torbjörn Oskar Caspersson (October 15, 1910 – December 7, 1997) was a Swedish cytologist and geneticist. ... Chromosomal translocation of the 4th and 20th chromosome. ... DiGeorge syndrome is also called Microdeletion 22q11 syndrome (del 22q11. ... Prader-Willi syndrome is a genetic disorder in which seven genes (or some subset thereof) on chromosome 15 are missing or unexpressed (chromosome 15q partial deletion). ...


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.


Beginnings of molecular cytogenetics

In the 1980s advances were made in molecular cytogenetics. While radioisotope-labeled probes had been hybridized with DNA since 1969, movement was now made in using fluorescently labeled probes. Hybridizing them to chromosomes preparations made using existing techniques came to be known as fluorescent in situ hybridization (FISH). 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. The 1980s decade refers to the years from 1980 to 1989, inclusive. ... The general structure of a section of DNA Deoxyribonucleic acid (DNA) is a nucleic acid —usually in the form of a double helix— that contains the genetic instructions specifying the biological development of all cellular forms of life, and most viruses. ... 1969 (MCMLXIX) was a common year starting on Wednesday For other uses, see Number 1969. ... Left panels show metaphase chromosomes before microdissection (top) and after a chromosomal band is removed (bottom). ...


Uses

translocation 9;11 associated with AML

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.g. imatinib mesylate in the presence of the Philadelphia chromosome). chromosome translocation 9;11 File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... chromosome translocation 9;11 File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... When normal cells are damaged beyond repair, they are eliminated by apoptosis. ... Although hematological malignancies are a form of cancer, they are generally treated by specialists in hematology, although in many hospitals oncology specialists also manage these diseases. ... Chromosomal translocation of the 4th and 20th chromosome. ... Imatinib is a drug used to treat certain types of cancer. ... Philadelphia chromosome or Philadelphia translocation is a specific genetic, chromosomal abnormality that is associated with chronic myelogenous leukemia (CML) and involves an exchange of material between chromosomes 9 and 22. ...


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. Mosaicism In medicine (genetics), a mosaic or mosaicism denotes the presence of two populations of cells with different genotypes in one patient, where usually one of the two is affected by a genetic disorder. ... Chromosomal translocation of the 4th and 20th chromosome. ...


Techniques

Routine analysis

Routine chromosome analysis refers to analysis of metaphase chromosomes which have been banded using trypsin followed by Giemsa. 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. An image of a newt lung cell stained with flourescent dyes during metaphase. ... Figure 1: Chromosome. ... // Chemistry and Function The enzyme trypsin cleaves proteins at the carboxyl side (or C-terminus) of the basic amino acids lysine and arginine except when these two residues are followed by proline. ... A complex of stains specific for the phosphate groups of DNA. Used in Giemsa banding (or G-banding) to stain chromosomes and often used to create a karyotype. ...


Slide preparation

Cells from bone marrow, blood, amniotic fluid, cord blood, tumor, and tissues (including skin, unbilical cord, liver, and many other organs) can be cultured using standard cell culture techniques in order to increase their number. A mitotic inhibitor (colchicine, colcemid) is then added to the culture. This stops cell division at mitosis which allows an increased yield of mitotic cells for analysis. 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. 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. Cord blood is human blood from the placenta and umbilical cord, which are left over after birth. ... Light micrograph of a newt lung cell in early anaphase of mitosis. ... Methanol, also known as methyl alcohol or wood alcohol, is a chemical compound with chemical formula CH3OH. It is the simplest alcohol, and is a light, volatile, colourless, flammable, poisonous liquid with a very faint odor. ... Flash point 43 Â°C R-phrases , S-phrases , , , US Permissible exposure limit (PEL) 10 ppm Supplementary data page Structure & properties n, εr, etc. ...


Analysis

Analysis of banded chromosomes is done at a microscope by a clinical laboratory specialist in cytogenetics (CLSp(CG)). Generally 20 cells are analyzed which is enough to rule out mosacism 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. The results are then given out reported in an International System for Human Cytogenetic Nomenclature 2005 (ISCN2005). It has been suggested that microscopy be merged into this article or section. ... Pathology (in ancient Greek pathos = feeling, pain, suffering and logos = discourse or treatise, i. ...


Fluorescent in situ hybridization

Interphase cells positive for a t(9;22) rearrangement
Interphase cells positive for a t(9;22) rearrangement

Fluorescent in situ hybridization refers to using fluorescently labeled probe to hybridize to cytogenetic cell preparations. fish bcr/abl cells File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... fish bcr/abl cells File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...


In addition to standard preparations FISH can also be performed on:

  • bone marrow smears
  • blood smears
  • paraffin embedded tissue preparations
  • uncultured bone marrow
  • uncultured amniocytes
  • cytospin preparations

Slide preparation

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. The slides are then washed to remove excess unbound probe, and counterstained with 4',6-Diamidino-2-phenylindole (DAPI) or propidium iodide. Ethanol, also known as ethyl alcohol or grain alcohol, is a flammable, colorless chemical compound, one of the alcohols that is most often found in alcoholic beverages. ... The general structure of a section of DNA Deoxyribonucleic acid (DNA) is a nucleic acid —usually in the form of a double helix— that contains the genetic instructions specifying the biological development of all cellular forms of life, and most viruses. ... Structural formula of DAPI DAPI or 4,6-diamidino-2-phenylindole is a fluorescent stain that binds strongly to DNA. It is used extensively in fluorescence microscopy. ...


Analysis

Analysis of FISH specimens is done in fluorescence microscopy by a clinical laboratory specialist in cytogenetics (CLSp(CG)). 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. For congenital problems usually 20 metaphase cells are scored. A Fluorescence Microscope is a light microscope used to study properties of organic or inorganic substances using the phenomena of fluorescence and phosphorescence instead of, or in addition to, reflection and absorption. ... Interphase is a phase of the cell cycle, defined only by the absence of cell division. ...


Future of cytogenetics

Advances now focus on comparative genomic hybridization arrays, and automated systems for counting the results of standard FISH preparations.


References

  1. ^  Tjio HJ, Levan A. The chromosome numbers of man. Hereditas 1956;42:1-6.
  2. ^  Lejeune J, Gautier M, Turpin MR. Etude des chromosomes somatiques de neuf enfants mongoliens. C R Acad Sci (Paris) 1959;248:1721-2.
  3. ^  Nowell PC, Hungerford DA. A minute chromosome in human chronic granulocytic leukemia. Science 1960;132:1497-1501.

Science is the journal of the American Association for the Advancement of Science (AAAS). ...

External links

  • Human Cytogenetics - Chromosomes and Karyotypes
  • Association for Genetic Technologists
  • Association of Clinical Cytogeneticists

  Results from FactBites:
 
Cytogenetics website (652 words)
The Cytogenetics unit was established as a diagnostic service at St James's Hospital in 1967 to provide a chromosome analysis service for the Yorkshire region.
Molecular Cytogenetics - This area of work is concerned with the investigation of chromosome abnormalities at the molecular level.
Cytogenetics is the study of chromosomes and chromosomal abnormalities.
Cytogenetics Summary (1839 words)
Cytogenetics is the study of the structure of chromosome material.
McClintock continued her career in cytogenetics studying the mechanics and inheritance of broken and ring (circular) chromosomes of maize.
Modern cytogenetics is generally said to have begun in 1956 with the discovery that normal human cells contain 46 chromosomes by Tjio and Levan
  More results at FactBites »

 
 

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