Source: Laboratory Course in Genetics

Operation method

basic program

Principle

Human somatic cells are diploid with 46 chromosomes (Figure 13-1). Females are 46,XX (Figure 13-2); males are 46,XY, and gametes are haploid, containing 23 chromosomes. Human chromosomes can be categorized into three groups according to the location of the mitotic site, namely, central mitotic chromosomes, subcentral mitotic chromosomes, and proximal mitotic chromosomes. It is difficult to recognize each chromosome without banding, therefore, according to the decreasing order of chromosome length and the location of the mitotic site, normal human chromosomes are classified into 7 groups of 24 types Group A: comprising chromosomes 1-3, which are large central mitotic chromosomes that can be distinguished from each other according to their size and the location of the mitotic site Group B: comprising chromosomes 4-5, which are large sub-central mitotic chromosomes that can be distinguished from each other according to their size and the location of the mitotic site Group B: comprising chromosomes 4-5, which are large sub-central mitotic chromosomes, which can be distinguished from each other according to their size and the location of the mitotic site Group B: includes chromosomes 4 and 5, which are large subcentral mitotic chromosomes that are not easily distinguishable from each other; Group C: includes chromosomes 6 to 12 and the X chromosome, which are medium-sized subcentral mitotic chromosomes, and the X chromosome is similar to chromosome 7; Group D: includes chromosomes 13 to 15, which are medium-sized proximal mitotic chromosomes with a follower; and Group E: includes chromosomes 16 to 18, which are the shorter subcentral mitotic chromosome (16) and the subcentral mitotic chromosome. Group E: includes chromosomes 16 to 18, which are short central (16) and subtelocentric (17, 18) chromosomes; Group F: includes chromosomes 19 and 20, which are short central mitotic chromosomes; Group G: includes chromosomes 21, 22, and the Y chromosome, which are subtelocentric chromosomes, and chromosomes 21 and 22 have follower bodies.

Materials and Instruments

Photomicrograph of human chromosomes
Millimeter ruler, tweezers, scissors, calculator.

Move

1. Measure each chromosome in the chromosome photo, calculate the relevant parameters, and complete the chromosome grouping analysis table.

2. According to the pairing of homologous chromosomes and the principle of human chromosome grouping, cut out the chromosomes and arrange them into a chromosome grouping diagram.

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