It is possible to define genotypes (set of genes of this organism) of parents, knowing genotypes of children, ideally several. Genotypes it is possible partially or even completely to make on phenotypes (sets of all signs and properties of an organism).
Instruction
1. Solve problems of definition of a genotype of parents with the known phenotypes on the following algorithm: 1. Define what signs are prepotent (are shown both in homozygous, and in a heterozygotic state), and what recessive (are shown only in a homozygous state). Try to make it on a statement of the problem. If it is impossible to determine by a condition, use special tables in which prepotent and recessive signs.2 are specified. Draw a statement of the problem schematically, using the standard designations: And, In – prepotent genes, and, b – recessive genes.3. From the scheme it will be visible with what missing genes are: prepotent or recessive. If genotypes of children are known, the task becomes simpler. Write down genotypes of children, then analyze what of couple of genes could go from mother or the father.
2. Sort out in more detail on the example of a task. Zakhar and Eliseus have gray eyes, and at their sister Aleftina - green. Mother of these children gray-eyed though both of her parents had green eyes. The gene responsible for color of eyes is located in not sexual chromosome (autosome). To define genotypes of parents and children. In the area of mother you see that gray color of eyes, is recessive sign since it is shown only in a homozygous state, i.e. at a meeting of two identical genes. In a heterozygotic state this sign forces out the prepotent gene which in this case is responsible for green color of eyes. Write down the decision so: And – the gene which is responsible for green color of eyes (prepotent), and – the gene which is responsible for gray color of eyes (recessive). Designate the known signs by letters.P: mother: aa father: __ G: mother: a father: __ F: aa, aa, AaDalee argue so: if sons have gray eyes (the sign which is shown in a homozygous state), one gene at them from mother, and another from the father, therefore, too is available for the father a recessive gene. If the daughter has a prepotent gene, then it precisely went from the father since at his mother cannot be (because of the fact that her eyes of gray color). Make the full scheme: P: mother: aa father: AaG: mother: a father: And, aF: aa, aa, AaZadacha is solved.