ii) A dominant disease called Ptosis in which affected individual cannot open eyes
fully is controlled by a dominant allele of gene P. A female with Ptosis, who
had father with Ptosis and normal mother, marries a normal man. The father of
affected female had 'normal mother. What is the genotype of parents of the
affected female? What portion of babies of this affected female will be
produced with Ptosis?
Answers
The portion of babies of the affected female to be born with Ptosis will be 50%.
Explanation:
Let us assume that the allele of gene P;
Dominant allele = P
recessive allele = p
Ptosis is a disease caused by allele P.
The Father of the affected female has Ptosis, which implies that he has at least one P allele.
The mother of the father of the affected female is normal. As we know, the offsprings get one allele from the mother and the other from the father. We can deduce that the father of the affected female, got the affected gene from this father. Hence the father of the affected female has one recessive allele 'p'.
The genotype of the father of the affected female = 'Pp'
As it is mentioned that the affected female has an affected father and normal mother, that means the genotype of the mother of the affected female is 'pp'.
The genotype of the affected female is 'Pp', she marries a normal male, implying that the genotype of the man is 'pp'.
Babies of this affected female born with Ptosis will be 50%.
