Solve problems by determining the genotype of parents with known phenotypes according to the following algorithm:
1. Determine which characteristics are dominant(manifest both in homozygous and in heterozygous condition) and which recessive(manifested only in the homozygous state). Try this to make the statement. If the condition to define does not work, use the special tables which list dominant and recessive traits.
2. Draw the problem schematically, using standard notation: a And b are dominant genes, a, b – recessive genes.
3. From the diagram it will be seen what are the missing genes: dominant or recessive.
If you know the genotypes of children, the task is simplified. Write down the genotypes of the children, then analyze which of the pairs of genes could come from mother or father.
Understand more info on the problem. The Zachary and Elisha grey eyes, and their sisters Aleftina green. The mother of these children, gray-eyed, though both her parents had green eyes. The gene responsible for eye color is located in that is not a sex chromosome (autosome and the). To determine the genotypes of the parents and children.
On the mother can see that the gray eye color is a recessive trait, because it manifests itself only in homozygous state, i.e. when two identical genes. In the heterozygous state this trait displaces the dominant gene, in this case, responsible for green eyes.
Record the decision And the gene for green eye color(dominant) and the gene responsible for gray eyes(recessive). Label known signs letters.
P: mother: father AA: __
G: mother: a father: __
F: aa, aa, Aa
Then argue this: if the sons grey eyes(the trait that shows up in a homozygous state), one gene from mother and another from father, therefore the father is also a recessive gene. If the daughter is present the dominant gene, then he just went from his father because his mother can not be(due to the fact that her eyes are gray).
Create a complete schema:
P: mother: father AA: AA
G: mother: a father: and, And
F: aa, aa, Aa
The problem is solved.