Question

The genotype of Rh+ person could be
A. RR
B. Rr
C. rr
D. Both A and B

Answer 1

Rh refers to the Rhesus antigen that is present in human blood.
If the antigen is present then it is called Rh-positive and if the antigen is absent it is called Rh-negative. A person who is Rh+ should have at least one R allele but it could have two alleles also.

Complete answer: The Rh factor carries genetic information and inherited from parents. The inheritance pattern is independent of the ABO blood type alleles.
There are 2 different alleles for the Rhesus factor referred to as R and r.
Biological parent donates one of their two R or r alleles to their child.
So, when a person is Rh+, it means he has one dominant allele that can produce Rh factor in the blood. Hence, the genotype can be Rr or RR.
rr indicates the recessive state i.e., Rh- person.

Additional information: A parent who is Rh- can only pass an Rh- allele to her son or daughter.
A parent who is Rh+ can only pass either an Rh+ (when the genotype is RR) or Rh- (when the genotype is Rr) allele to his son or daughter.
The offspring should have Rh+ when the mother is Rh- and the father is Rh+ with genotype RR. The offspring should have Rh- when the mother is Rh- and the father is Rh+ with genotype Rr. Rh+ is a dominant character and hence is expressed in both homozygous and heterozygous genotypes.

Hence, the correct answer is option D. Both A and B.

Note: During pregnancy, problems can occur if the mother is Rh-negative and the father is Rh-positive. This couple can result in an Rh-positive child that grows in an Rh-negative mother’s womb. When the blood of mother and fetus mixes it results in the production of anti-Rh factors that help to coagulate the child’s blood.
This condition is called erythroblastosis foetalis. In this clinical condition, the child dies in the womb and the mother’s life is also at risk.