Question

Rh factor is present in
(a) All vertebrates
(b) All mammals
(c) All reptiles
(d) Man and Rhesus monkey only

Answer 1

Rh factor is a part of the Rh blood group system, and it refers to the multiple Rh blood group antigens present on the red blood cells. These factors are specific to some species of animals, especially warm-blooded mammals.

Complete step by step answer:
- Rh factor, or ‘Rhesus factor’, is a group of antigens that determine the blood group of human beings is Rh-positive or Rh-negative. If a person’s blood group is O +ve, the person has no A or B antigens and Rh factors on the RBCs.
- The factor was discovered first when Landsteiner and Weiner immunized a rabbit with blood in Rhesus macaques, hence the name.
- The antibodies are known as anti-Rh.
- These factors have been discovered only in humans and Rhesus monkeys.

Additional Information:
- The five main Rhesus antigens are C, c, D, E, and e.
- A person’s positive and negative Rh factor does not affect their health. However, the factor has an important role in pregnancy. If a pregnant woman is Rh-negative and the child is Rh-positive (which occurs from conception with an Rh-positive male) , the mother’s body will produce antibodies against that of the child during the fetal or newborn stage. This condition is known as erythroblastosis foetalis.
- There are vaccines available which can be provided to the pregnant female to prevent the condition.
So, the correct answer is ‘Man and Rhesus monkey only’.

Note:
- Rh factor was earlier considered to be identical in Rhesus macaques and human beings, and was later disproved.
- Rh factor can be detected by a simple blood test, the same used for detecting the ABO blood group.