Question

a) Why is the human ABO blood group gene considered a good example of multiple alleles?
b) Work out a cross up to F1 generation only, between mothers with blood group A (homozygous) and the father with blood group B (Homozygous). Explain the pattern of inheritance exhibited.

Answer 1

In human beings four types of blood groups are present that is A,B, AB, and O. Sometimes during the blood transfusion the serious reaction takes place like haemolysis of red blood cells and agglutination. These all occur due to antibodies the recipient does not accept the blood of another person.

Complete answer:
a) The blood group ABO is set by I genes and this I gene having the three alleles (IA, IB, And IO).
So, that is the reason ABO blood group genes have multiple alleles.

b)

So the blood group is AB.

Blood group A having antigen A and antibody B.
Blood group B having antigen B and antibody A.
Blood group AB having the antigen A and B but no antibodies.
Blood group O having no antigen but both the antibodies.
Karl Landsteiner found the four types of blood.

Note: Person of blood group O is called universal donors. They can donate their red blood cells to any other blood group.

Person of the blood group AB positive is called a universal recipient. They can receive red blood cells from any other blood group.
Person of the blood group AB negative is called a universal plasma donor. They can donate plasma to any other blood group.