Question

How does the gene I control ABO blood Sroups in humans ? Write the effect the gene has on the structure of red blood cells.

Answer 1

Gene has three different alleles  l^A, I^B, i.

- I^A produces A type of sugar / Antigen  → A group I^B produces B type of sugar / Antigen →  B group 

 - i - No sugar  - O group. 

-  Structure  -  sugar polymers protrude from the surface of plasma membrane of RBCs.

Detailed Answer : 

In humans, the ABO blood groups are controlled by a gene called I. It has three alleles, namely I^A, I^B and i. A person possesses any two of the three alleles. I^A aid I^B are dominant over allele i. But I^A and I^B are co-dominant as they express themselves equally and independently When present together. These three alleles yield six different combinations which give four type of blood groups. The allele pair I^AI^A or I^A i  yield Blood groups  A, I^B I^B or l^B i  the blood group B,  I^A I^B is blood group AB, and ii is blood group O. 

The plasma membrane of red blood cells has sugar polymers that protrude out from its surface and the kind of sugar is regulated by the gene 'I' of ABO blood group. The alleles I^A and I^B produce A and B types of sugar, while i does not produce any sugar.