Question

Study the pedigree chart given below, showing the inheritance pattern of blood group in a family:

Answer the following questions:
(a) Give the possible genotypes of individual 1 and 2.
(b) Which antigen or antigens will be present on the plasma membranes of the R.B.Cs of individuals ‘5’ and ‘8’?

Hint:

Blood group inheritance follows codominance (A and B alleles) and simple recessiveness (O allele). Genotype must be inferred from both phenotype and offspring data.

Answer 1

[(a)]
Individual 1 (B): Possible genotype = \( I^B I^O \)
Individual 2 (A): Possible genotype = \( I^A I^O \) (Since their child (individual 8) has blood group O, both parents must carry the \( I^O \) allele.)
[(b)]
Individual 5 (AB): Antigens present = A and B antigens
Individual 8 (O): Antigens present = None (no A or B antigen present on RBC membrane)