Question

Assume a man with type AB-positive blood has a biological child with a woman who has type O-negative blood. Answer the following questions. Use letters ABO or D/d for the alleles.

a) Write the man's possible genotype(s) for both characteristics.

b) Write the woman's possible genotype(s) for both characteristics.

c) What is the probability of the child having type A-negative blood?  

Answer 1

ABO locus determines the blood group, IA, IB and i alleles at the ABO locus determine blood group, when both IA and IB alleles are present the blood is AB type, and when both alleles are i, then blood type is O, and if the genotype is IAi or IAIA-blood type is A, and when the genotype is IBIB or IBi the blood type is B

D locus determines whether the blood has Rh antigen or not, D is dominant to d, DD, Dd are Rh posiitve and dd is Rh-negative

a) man has AB +ve blood,

so the possible genotypes are IAIBDD, IAIBDd.

b) woman has O negative blood so her genotype is iidd.

c) to get a child with negative blood group the genotype of the man has to be IAIBDd, so that he can produce gamete with d allele, the genotype at the D locus of the child with negative blood group is dd, dd child inherits d allele from both parents.

IAIBDd * iidd

	IAD	IAd	IBD	IBd
id	IAiDd ( A positive)	IAidd ( A negative)	IBiDd ( B positive)	IBidd ( B negative)

probability of the child having type A-negative blood = number of children with A negative blood/total number=1/4