This experiment requires students to master the principles and methods of plotting genetics graphs, learn how to process data for experimental results, and further deepen their understanding of the concepts of recombination values, genetics graphs, double exchange values, concurrency, and interference. Source: Laboratory Course in Genetics
Operation method
three-point intersection method (math.)
Principle
This experiment verifies that genes are arranged in a straight line on chromosomes by the exchange behavior of three non-alleles on the same chromosome. First, wild-type Drosophila was crossed with three recessive Drosophila (white-eyed, small-winged, and burnt bristles) to make a three-factor hybrid, and then the female hybrids were tested with the three-recessive individuals, and eight different phenotypes could be obtained due to the exchanges of genes in the tested progeny, and the distance and order of the three interlocking genes on the chromosome could be measured in a single experiment after the data processing, and the interlocking diagrams could be plotted.
Materials and Instruments
Drosophila melanogaster strain: wild-type Drosophila ( + + + ): red eyes, long wings, straight bristles Drosophila melanogaster triple cryptic ( w msn3 ): white eyes, small wings, bristle bristles Move 1. In order to have enough Drosophila for the hybridization experiments, virgin and male flies of wild-type and triple-recessive strains can be collected and cultured separately 2-3 d before the experiments. 2. Hybridization was carried out according to the following combinations. 5 pairs per bottle, labeled and incubated at 25℃. 3. 7d later, the F1 flies were labeled and incubated at 25℃. 3. After 7d, the pupae of F1 generation appeared and released the parents. 4. 4. After 4-5d, the F1 generation of adult flies will appear. Observe the phenotype and sex of the F1 of the two combinations of forward and reverse crosses, and observe the companion inheritance. 5. 5. Select a number of pairs of Drosophila from the F1 generation (positive and negative combinations should not be mixed up) and put them into new culture bottles to continue crossbreeding, with 5-10 pairs in each bottle. 6. After 7d, the F2 generation pupae appeared and released the parents. 7. 7. After 4-5d, the F2 generation of adult flies hatch gradually and can be observed and counted. Eye color, wing shape and bristle morphology were examined with a binocular microscope. The orthogonal and inverse combinations were counted separately, and only the males were counted in the orthogonal combination. Each type of Drosophila was counted separately. The second batch was examined and counted two days later, and was examined consecutively for 8-10d, i.e. 3-4 times. At 25℃, it is reliable within 10d since the first batch of Drosophila hatched, and the F3 generation may appear later. At least 250 fruit flies per group should be counted. In general, there should be 8 phenotypes in the F2 population, of which 2 are parental types (more numerous), 4 are single-exchange types, and the 2 least numerous are double-exchange types. 8. Record the statistics in the following order (all the individuals of the backcross combination are combined with the statistics of the males of the orthologous combination). For more product details, please visit Aladdin Scientific website.
Ether Cornstarch Agar Brown sugar Yeast powder Propionic acid
Stereoscopic dissecting mirror Constant temperature incubator Balance Culture and anesthesia bottles Brushes and white porcelain plates