Question

ABO blood grouping is determined by three alleles. Possible genotypes and phenotypes are

• A. 3, 1
• B. 6, 4
• C. 4, 6
• D. 9, 7

Answer 1

The correct option is B 6, 4

ABO blood group in human beings is first discovered by Landsteiner. The fourth blood group, AB was discovered by de Castello and Stein. Bernstein showed that these groups are controlled by three alleles – I^A,I^B and I^O/i. These alleles are autosomal and follow the Mendelian pattern of Inheritance. Alleles I^A, I^B produce a slightly different form of sugar while I^O does not produce any sugar. Because humans are diploid organisms, each person possesses any two of the three ‘I’ gene alleles. I^A and I^B are completely dominant over I^O, but when I^A and I^B are present together, they both express their own types of sugar, thus, behaving as codominant alleles.

So, the correct option ‘6,4’.