Problem

Date: 2015-10-07; view: 472.

Analyze the results of the crossing of two heterozygous individuals of generation F1. Consider 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.

А а female gamete♀

During the solving of problem count the number of possible combinations of gametes in the zygote. What is the numerical ratio of genotype, resulting in F2? Great interest originates from the study of external, phenotypical features of F2. How many different phenotypes occur in the F2 during the crossing, and which numeric ratio they will have?

Analysis of behavior during crossing of different varieties of peas allowed Mendel to formulate the laws of heredity played an important role of genetics. Study monohybrid crossing can get acquainted with Mendel's two laws. First law – the law of dominance or first dihybrid generation features of uniformity. It was possible to verify that after crossing of yellow seed and green seed pea F1 individuals have only yellow seeds. The second law of Mendel law of features splitting shows that splitting of dominant and recessive genes in a 3:1 ratio occurs in the second hybrid generation. During the solving of proposed problem, you could be convinced that appearance of three individuals with a yellow color and one individual with a green colored seeds of in F2 is possible.

Laboratory work №2