Co-dominance in Genetics

Co-dominance in Genetics

• Co-dominance results in the F₁ generation exhibiting traits from both parents, contrasting with classical dominance or incomplete dominance.
• Human ABO blood type is a prime example of co-dominance, controlled by the gene I.
• The gene I has three alleles: IA, IB, and i.
• Alleles IA and IB produce distinct forms of sugar on the surface of red blood cells, while allele i results in no sugar production.
• In diploid organisms like humans, an individual inherits two of the three possible alleles, leading to various combinations.
• Alleles IA and IB are completely dominant over allele i, meaning that when combined with i, only the sugar-producing allele is expressed.
• When both IA and IB are present, both sugars are produced, demonstrating co-dominance.
• This leads to red blood cells having both A and B sugars when IA and IB are paired.
• The presence of three alleles allows for six different combinations, resulting in six distinct genotypes for ABO blood type.
• Six possible genotypes lead to four observable phenotypes: A, B, AB, and O blood types.