Question

URGENT!! In certain varieties of chicken, an allele for black feathers (IB) is co-dominant with an allele for white feathers (IW). Part A: Predict the phenotype that will be expressed by a chicken that is heterozygous (IBIW) for feather color. Part B: Suppose a solid white hen (IWIW) mates with a solid black rooster (IBIB). Predict the percentage of their offspring that will express a co-dominant phenotype. In your answer, be sure to explain the reasoning behind your prediction. Part C: Describe how co-dominance is different from incomplete dominance.

Answer 1

A heterozygous (IBIW) chicken will have speckled feathers due to codominance. When a IWIW hen and IBIB rooster mate, all offspring will be 100% speckled. Co-dominance allows both alleles to be fully expressed, unlike incomplete dominance which produces a blend of parental traits.

Step-by-step explanation:

Part A: The phenotype expressed by a chicken that is heterozygous (IBIW) for feather color would be speckled, with both black and white feathers due to codominance, where both alleles are fully expressed.

Part B: If a solid white hen (IWIW) mates with a solid black rooster (IBIB), all of their offspring will be heterozygous (IBIW) and thus 100% of them will express the co-dominant phenotype of speckled black and white feathers. This is because each parent contributes a different allele, IB from the rooster and IW from the hen, to each offspring.

Part C: Co-dominance differs from incomplete dominance in that in co-dominance, both alleles are fully and equally expressed in the phenotype, as in the ABO blood group system in humans, or the speckled feathers of the chicken. In incomplete dominance, the heterozygote shows a blend of the two parental phenotypes, such as the pink flowers of a snapdragon, which result when a red-flowering plant is crossed with a white-flowering plant.

Answer 2

A) black and white strips on the feathers

B) 100 %

C) Co-dominance allows expression of two different traits individually without blending/mixing while incomplete dominance allows expression of a new trait by blending the two parental traits.

Step-by-step explanation:

Part A-

Since the two alleles i.e an allele for black feathers (IB) and an allele for white feathers (IW) are co-dominant. Thus, a heterozygous individual that has both IB and IW allele will have black and white strips on the feathers.

Part B-

A solid white hen (IWIW) and solid black rooster (IBIB) mates , then the following offspring will be produced

IBIW, IBIW, IBIW, IBIW

Out of four offspring, all are heterozygous and thus they are co-dominant.

Thus, 100% offspring express a co-dominant phenotype.

Part C-

Co-dominance allows expression of two different traits individually without blending/mixing while incomplete dominance allows expression of a new trait by blending the two parental traits.