Question

In humans, Rhesus conditions can arise when

• A. Father is Rh and mother is Rh${}^{-}$
• B. Father is Rh${}^{-}$ and mother is Rh
• C. Either father or mother is Rh${}^{+}$
• D. Either father or mother is Rh${}^{-}$

Answer 1

The correct option is A Father is Rh and mother is Rh${}^{-}$

• Rh status of a person is determined by Rhesus D antigen present on the RBCs.
• There are two alleles for the Rh factor- Rh+ and Rh-.
• The Rh+ person has at least one Rh+ allele i.e the genotype can either be Rh+/Rh+ or Rh+/Rh-, Rh- person has a genotype of Rh-/Rh-.
  
• An Rh- mother can only pass an Rh- allele to her son or daughter.
• Whereas, Rh+ father can pass either an Rh+ or Rh- allele to his son or daughter.
  
• Thus, Rh+ child is born when the mother is Rh- and father is Rh+.
• The correct answer is 'Father is Rh and mother is Rh−'.