Problem

Date: 2015-10-07; view: 508.

For genetic research fruit fly Drosophyla melanogaster object is convenient. It bred on an artificial medium, closed with a cotton swab cups height of 10 cm, diameter 4 cm. Composition of nutrient medium: water 100 g, 12.5 g of raisins, boiled potatoes 37.5 g, agar 2.0 g, 5 g compressed yeast. Preparation: Pour into the boiling water, put the agar-agar, and after dissolving of it other thoroughly mashed products are added. The mixture was simmered for 15-20 minutes. Ready media is poured into a glass fiber 1-1,5 cm. After getting cool, it becomes like thick jelly. After that, on its surface is applied with a brush, liquid yeast. A day after making the environment in glasses can be planted flies. Then the cups with the flies are placed in an incubator. Optimal for the development of Drosophila is temperature 25-26. At this temperature, their entire life cycle is 9-10 days.

In order to obtain a sufficient number of flies for the simultaneous viewing of the parents, first and second generation hybrid generation in dihybrid crossing homozygous parents need to make a crossing for 22-24 days prior to the occupation. This requires at least 2-3 cups. For the parental generation mating virgin females are needed. Recently hatched females have weak pigmentation and no wings. In each cup put two females and three males.
For this practice it is convenient to use the crossing of two mutations - dumpy and ebony. At the same care that captured a male who is female, as involved in mating genes are not linked to sex. Flies distribute to students in the anesthetized state. The latter has already done in class with stains. In the simplest case - common test tubes with corks on the inner surface of the pins that attach the pieces of cotton wool soaked in ether. Flies of the cups are available in stains that clog. When the flies cease to move, they poured on the subject of glass. All manipulations with Drosophila should be done with great caution, take them with forceps at the wing or leg. Students should give tweezers with sharp edges, as well as the plate glass of milk or white boxes.

Analyze the results of the crossing of two heterozygous individuals of generation F1. Please note that during the formation of germ cells in meiosis of F1 hybrids in each germ cells can enter only one gene from allelomorphous pair. As a result, 50% of gametes will contain the dominant gene - A, 50% of the gametes - a recessive gene - a. In order to visualize all the combinations that arise in crosses between individuals of a F1, draw a "grid". Along the upper part of the lattice make a note of all possible types of eggs, and along the left - all possible types of sperm. Cells of the lattice fill combinations of gametes that occur at fertilization.