Question

In a diploid organism, there are three different alleles for a particular gene. Of these three alleles one is recessive and the other two alleles exhibit co-dominance. How many phenotypes are possible with this set of alleles?

• A. 3
• B. 6
• C. 4
• D. 2

Answer 1

The correct option is C 4

According to the question, out of three alleles of a gene, one is recessive. Let’s suppose that c is recessive to both A and B alleles. The total possible genotypes with these three allele will be AA, BB, Ac, Bc, cc and AB. “AA” and “BB” genotypes will express their respective pheontypes, let’s suppose x and y phenotypes respectively. As c is recessive to A and B; genotypes Ac and Bc will also produce x and y phenotypes respectively. The “cc” genotype will produce recessive phenotype “z”. As “A” and “B” are co-dominant, the genotype “AB” will express both alleles and the phenotype will be “xy”. Thus, three alleles of a gene with given recessive-dominance relationship will produce total four phenotypes. Correct option is C.