In humans, brown eye color dominates over blue, and the ability to use the right hand better dominates over left-handedness. a) a diheterozygous brown-eyed right-hander married a heterozygous brown-eyed left-hander. Their first child is a blue-eyed right-hander. What is the probability of having a second child with the same combination of traits? what are the genotypes of the parents and possible offspring?
Let the gene that leads to the development of brown eyes be designated as P, and the gene for blue eyes as p. Let the left-handed gene be l and the right-handed gene L.
The male is conditionally diheterozygous, write it as PpLl. It produces four types of spermatozoa – pl, PL, pL, Pl.
Left-handed woman, heterozygous for the gene for eye color – Ppll. She is homozygous for the left-handedness gene, otherwise this trait would not appear in her. It produces two types of oocytes – Pl, pl.
The possible offspring of this married couple will be represented by the options:
brown-eyed children, predominantly using the left hand (2Ppll, PP ll);
brown-eyed children, predominantly using the right hand (PP Ll, 2PpLl);
blue-eyed children, predominantly using the left hand (ppll);
blue-eyed children, predominantly right-handed (ppLl).
The probability of having a second blue-eyed right-hander in the family is 1 in 8, or 12.5%.