Question

1. The MN blood group system is under the control of an autosomal locus found on chromosome 4, with two alleles designated L^M and L^N. The blood type is due to a glycoprotein present on the surface of red blood cells, which behaves as a native antigen. L^M and L^N are codominant and heterozygotes express both antigens and have blood type MN.

In the following crosses, what will be the genotypes and phenotypes, and their ratios, in the offspring?

a. L^ML^M   X   L^ML^N

b. L^NL^N   X   L^NL^N

c. L^ML^N   X   L^ML^N

d. L^ML^N   X    L^NL^N

e. L^ML^M    X    L^NL^N

Answer 1

We can draw a punnett square to find out the possible genotypes and phenotypes. Please see the image attached. M type blood will be present only when both alleles are M. Similarly, N type blood will be there when both alleles are N. When alleles M and N both are present, MN blood type will be formed since both these alleles are codominant.