Study the given pedigree chart and answer the questions that follow:
(a) Is the trait recessive or dominant?
(b) Is the trait sex-linked or autosomal?
(c) Give the genotypes of the parents shown in generation I and their third child shown in generation II and the first grandchild shown in generation III.
OR
Haemophilia is a sex-linked recessive disorder of humans. The pedigree chart given below shows the inheritance of Haemophilia in one family. Study the pattern of inheritance and answer the questions given.
(a) Give all the possible genotypes of the members 4, 5 and 6 in the pedigree chart.
(b) A blood test shows that the individual 14 is a carrier of haemophilia. The member numbered 15 has recently married the member numbered 14. What is the probability that their first child will be a haemophilic male.? Show with the help of Punnett square.
(a) The given trait is dominant as it is getting expressed in all the generation.
(b) The trait is autosomal because the male and female progeny of 2nd generation is equally getting affected by the disease or trait.
(c) Let Mm (dominant) denote the one affected by trait.
Genotype of parents shown in generation 1: Mm (affected male) and mm (healthy female)
Genotype of 3rd child in generation 2: Mm (affected male child)
Genotype of 1st grandchild in generation 3: Mm (affected female).
OR
(a) Let XX denote female, and XY denote male.
The genotype of 4: XXh (XXh shows that the female is a carrier of haemophilia as Xh is suppressed by another X gene, h show the gene for haemophilia.
The genotype of 5: XhY (XhY shows a haemophilia affected male as Xh is expressed dominantly over gene Y.)
The genotype of 6: XY (XY shows a healthy male; also male cannot act as a carrier of the haemophilic gene.)
(b) Genotype of individual 14 is XhX (female carrier of haemophilia)
and of individual 15 is XY (healthy male).
The probability of their first child being a haemophilic male is: 1/4
Punnet square:
