Question

Study the given pedigree chart and answer the queation that follow.

(a) In the trait recessive or dominant ?
(b) Is the trait sex-linked or autosomal ?
(c) Give the genotypes of the parants in generation I and of their third and fourth child in generation.

Answer 1

(a) the trait is recessive.
(b) the trait is Autosomal recessive trait.
(c) This is an autosome linked recessive trait that can be transmitted from parents to the of offspring when both the partners are carrier for the gene (or heterozygous).
The disease is controlled by a single pair of allele, `Hb^(A) and Hb^(S)` . Out of the three possible genotypes only homozygous individuals for `Hb^(S) (Hb^(S) Hb^(S))` show the diseased phenotype Heterozygous (Hb Hbs) individuals appear unaffected but they are carrier of the disease as there is 50% probability of transmission of the mutant gene to the progeny.
Genotype I generation - Aa and Aa
Genotype of generation II of third child is aa and fourth child is Aa.