In the family of parents who have developed the ability to assimilate the amino acid phenylalanine, but have a visual defect – myopia, two children are born: one child is myopic, like his parents, but with no phenylketonuria disease; the second – with normal vision, but suffering from phenylketonuria. Determine what are the chances for children born in this family to be just like that, if it is known that the development of myopia is controlled by a dominant gene, and the presence of a disease such as phenylketonuria is controlled by a recessive gene, and both pairs of genes are located in different pairs of autosomes.
A – assimilate phenylalanine, and – phenylketoniria.
B – myopia, b – normal vision.
Parents: AaBb x AaBb,
Gametes: AB, Ab, ab, ab x AB, Ab, ab, ab.
Children: A * B *, aabb. Any of the alleles can be in place *.
With such a crossing, the phenotype splitting in the offspring is always 9: 3: 3: 1:
9 nearsighted with phenylalanine metabolism, 3 nearsighted with phenylketonuria, 3 with normal vision using phenylalanine, 1 with normal vision and phenylketonuria. There are 16 options in total.
The probability that children will be nearsighted, absorbing phenylalanine is 9/16, and with normal vision and phenylketonuria – 1/16.