Chromosome structure variation experiment

Summary

Understand that when chromosome structure is mutated, chromosome bridges or chromosome breaks can be observed in mitotic cells at later stages, and micronuclei can be observed in interphase cells.

Operation method

Chromosome structure variation experiment

Principle

There are four main types of chromosome structural variants: deletion, duplication, inversion and translocation. They occur as a result of breaks between homologous or non-homologous chromosomes followed by erroneous rejoining. Heterozygotes with various structural variants often exhibit abnormal cytological behavior during cell division and can be identified cytologically. In meiosis, the "deletion ring" of deletion heterozygotes, the protruding ring or tumor of chromosomes in reduplicated heterozygotes, the "inversion ring" or late chromosome bridge in inverted heterozygotes, and the "cross shape" of the "cross shape" in translocation heterozygotes are all observed during meiosis. "cross-shaped" unions or terminal "tetrasomal rings", "tetrasomal chains" and "figure-of-eight rings". In mitotic cells, there are chromosome bridges, chromosome fragments, and micronuclei in interphase. Chromosomal structural variations generally lead to partial sterility or semi-sterility of pollen and ovules, variation of inherited traits, pseudodominance, pseudo-linkage, dosage effect, positional effect and other genetic consequences of altered gene-linkage relationships, which may result in the death of the individual in severe cases. Chromosome behavioral observations and genetic effects experiments corroborate each other to identify the type of chromosome structural variation.

Materials and Instruments

Broad beans
Magenta acetate Modified phenol magenta Alcohol anhydrous 70% alcohol Hydrochloric acid
Microscope Incubator Analytical balance Water bath Alcohol lamp Scissors Tweezers Dissecting pins Slides Coverslips Filter paper Pencil Labeling paper Glue

Move

I. Materials and equipment

1. Experimental materials:

Dry seeds of broad bean (vicia faba, 2n = 12)

2, Experimental apparatus and utensils:

Microscope, incubator, analytical balance, water bath, alcohol lamp, scissors, tweezers, dissecting needles, slides, coverslips, filter paper, pencil, label paper, glue

3, Drugs and reagents:

Magenta acetate, modified phenol magenta, anhydrous alcohol, 70% alcohol, 1N hydrochloric acid,

II. Experimental methods and steps

1、Material preparation

Selected with strong vitality of broad bean dry seeds, by 45 Glenn cobalt 60 irradiation (or with plant mutagens, etc.) treatment. Soak the seeds for 24 hours, and then placed on an enameled plate flattened germination, covered with three layers of gauze insulation, at 20 ℃ on the culture, to be the root length of 1 ~ 2 cm, cut the tip of the apical root tip of about 5 mm in the Carnot's fixative for 0.5 hours, and then replaced with 70% alcohol preservation of standby.

2、Dissociation

Take out the fixed spare root tip, cut the part with phloem tissue about 1~2 mm, (remove the root crown and elongation zone cells) in 1NHCl dissociation for 10-20 minutes. Then wash the material with distilled water to remove hydrochloric acid and prepare for preparation and staining.

3、Staining preparation

Take a dissociated broad bean root tip and place it in the middle of the slide, press the two slides against each other in a cross shape, then uncover it, put a small drop of stain (magenta acetate or modified phenol magenta) on each part of the material, and then press the slide with a coverslip (see Experiment 1).

4, Microscopic examination:

Observe chromosome bridges and chromosome breaks in late mitotic cells, and micronuclei in interphase cells.

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