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The term karyotype was first proposed by Soviet scholar TA Levzky and others in the 1920s. The development of karyotype analysis has played an important role in promoting three technologies. First, the low-osmotic treatment technology discovered by American Chinese cytologist Xu Daoju in 1952 has made the chromosomes of metaphase cells well dispersed and easy to observe. Second, colchicine The application facilitates the cell division phase in the concentrated phase; the third is that the plant lectin (PHA) stimulates the transformation and division of blood lymphocytes, making it possible to observe the chromosomes of animals and humans by blood culture methods.
Karyotype refers to the phenotype of the genome in the middle of mitosis, including the number, size and morphological characteristics of chromosomes. Karyotype analysis is the process of grouping, queuing, pairing and performing morphological analysis based on the measurement and calculation of chromosomes. Karyotype analysis is of great significance for exploring the mechanisms of human genetic diseases, species phylogenetic relationships and evolution, and identification of distant hybrids. An image in which all chromosomes of a genome are drawn one by one according to their characteristics, and then arranged in terms of length, shape, and the like, is called a karyotype pattern, which represents a karyotype pattern of a species.
In 1960, at the Denver meeting, a draft system for naming standards for human mitotic chromosomes was proposed, which laid the foundation for all subsequent naming methods. In 1963, at the London meeting, the seven letters of A, B, C, D, E, F, and G proposed by Patan were officially approved to represent the classification of seven groups of chromosomes. In 1966, at the Chicago meeting, a standard naming scheme for human genomes and asymmetry shift symbols was proposed.
Group A (1-3)
No. 1: The largest central centromere chromosome with a long scar near the filament.
No. 2: The largest sub-central centromere chromosome.
No. 3: Central centromere chromosome, one third smaller than No. 1.
Group B (No. 4-5): It is a large sub-central centromere chromosome, which is difficult to distinguish.
Group C (6-12, X): medium-central central centromere chromosomes, difficult to distinguish from each other.
6, 7, 9, 11: The centromere is slightly near the center.
8, 10, 12: Deviation from the center.
No. 9: q has a scar.
X is between 6 and 7.
Group D (No. 13-15): medium-central centromere chromosome, p often has a satellite.
Group E (No. 16-18)
No. 16: Medium central centromere chromosome with a scar on q.
No. 17: Smaller, near central centromere chromosome.
No. 18: Smaller, near central centromere chromosome, p is shorter than 17th.
Group F (No. 19-20): Small central centromere chromosomes that are not easily distinguishable from each other.
Group G (21-22, Y): a small proximal centromere chromosome.
21, 22: p often has a body, q is often branched and difficult to distinguish from each other.
Y:p has no satellite, q is usually parallel.
Experimental reagent
Geimsa staining solution, etc.
Photomicroscope, micro micrometer, dyeing cylinder, hair dryer, etc.
Human peripheral blood lymphocyte chromosome specimen
1. Put the human peripheral blood lymphocyte chromosome specimen into the dyeing tank and stain with Geimsa staining solution for 10-15 minutes → Punch in the water plastic cup → air dry → Microscopic examination: The standard of the cells is:
(1) The cells are intact, the outline is clear, and the chromosomes are distributed on the same level.
(2) The chromosome morphology and distribution are good.
(3) It is best not to overlap, even if there is an individual overlap, it must be clearly identified to avoid mistakes.
(4) The observed cells are in the same mitotic stage, that is, the degree of chromosome helix or the length of the chromosome is roughly the same.
(5) There are no discrete single or multiple chromosomes around the observed cells to avoid affecting the counting.
3. Karyotype analysis: All chromosomes in a cell are arranged in a certain order, representing the chromosome composition of all cells of an individual, including number, shape, size, etc., divided into A, B, C, D, E, Seven groups of F, G, and a group of sex chromosomes.
Group type: The karyotype is expressed in the form of a pattern diagram, representing the chromosome composition of a species.
4. Complete karyotype analysis.
Precautions
Micrograph analysis:
Chromosome count; chromosome measurement;
Relative length = single chromosome length / total number of single chromosomes × 100
Arm ratio = q / p
Centromere index = p / (pq) × 100