Question

O blood group is the universal donor because the blood has
(a)Antigen A
(b)Antigen B
(c)Both antigens A and B
(d)No antigens

Answer 1

Hint: O blood group is known as the universal donor because they can donate blood to all the other blood groups which are A, B, and AB. Whereas the blood group AB is known as the universal recipient as it can receive blood from all blood groups.

Complete Answer:
O blood group is the universal donor because the blood has no antigens present in it. Because there are no antigens present on the plasma membrane of the RBC in blood, antibodies A and B both are present in the plasma of such people. These antibodies will destroy and clump RBC cells that contain antigens A or B on them. All the blood groups A, B, and AB have antigens A or B on their membrane and thus cannot donate blood to people with O blood group.

Additional information:
Let us understand the process of ABO blood grouping in detail.
-A person with blood group A has antigen A and antibody B in his blood and can donate to blood groups A and AB
-A person with blood group B has antigen B and antibody A in his blood and can donate to blood groups B and AB.
-A person with blood group AB has both antigens A and B but no antibodies in his blood and thus such a person can accept blood from any blood group as there as no antibodies to attack the other blood.
-A person with blood group O has no antigens but contains both antibodies A and B and thus can donate blood to any other blood group.

So, the correct option is ‘No antigens’.

Note:
-There are three alleles coding for the blood group in humans and thus it comes under multiple allelism.
-The allele ‘$I^A$’ causes A antigen, allele ‘$I^B$’ causes B antigen whereas allele ‘i’ results in no antigen.
-The alleles ‘$I^A$’ and ‘$I^B$’ are completely dominant over ‘i’ but codominant over each other.
-Another type of blood grouping is seen in humans known as the Rh blood grouping.