Describe the nature of inheritance of the ABO blood group in humans. In which ways does this inheritance differ from that of height of the plant in garden pea?
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Answer:
A classic example of co dominance is Human ABO groups. ABO blood groups are controlled by the gene I. The plasma membrane of the red blood cells has sugar polymers that protrude from its surface and the kind of sugars is controlled by the gene. The gene I has three alleles IA, IB and i. The allele IA and IB produce a slightly different sugar form while allele ′i′ doesn't produce any sugar. As human beings are diploid an individual can have any two of the three alleles. IA and IB are co dominant while IA and I are dominant over i. When IA is present in both homozygous or heterozygous condition, the blood group will be "A" with IAIA or IA i conditions.
When IB is present in IBIB or IBi condition, it produces the blood group “B”. When IAIB come together, it results in blood group “AB”. When ii is present together, it results in blood group “O”.
In pea plants tallness is completely dominant over dwarfness. In blood groups, gene IA and IB are codominant. They both express together when they occur together resulting in a new phenotype.
So ABO blood grouping is the example of Co-dominance and is also an ex. of Multiple Alleles(Ia,Ib,i)...so co-dominance is the exception of the Law of Dominance and multiple alleles is ex of intragenic interactions....so by this way is differs from the pea plant bcz pea plant follows the mendelian rules....