Write a short note on multiple alleles considering the example of human blood group.

Explanation

(ii) Multiple alleles:
(i) 1) More than two alleles of a gene occupy the same locus on chromosomes.
2) Multiple alleles arise by mutation of wild type of gene.
3) Different alletes may show dominant recessive, codominane, incomplete dominance.
4) Multiple alleles do not undergo crossing over.
Example: ABO blood group.
The gene I controls ABO blood groups. It has three alleles `I^(A), I^(B)` and i.
The alleles `I^(A), I^(B)` produce different protein antigen but I does not produce any antigen.
The alleles `I^(A),I^(B)` are codominants and are dominant over i.
There are six types of genotype and four type of phenotype.