Question

17 multiple choice 1 point in a regular dihybrid cross, a ratio of 9:3:3:1 is observed. in one experiment, a researcher observed a ratio of 9:3:4. this is likely a result of incomplete dominance codominance epigenesis epistasis

Explanation:

1. Recall the concepts:

• Incomplete dominance: Results in intermediate phenotypes, not ratio modification like 9:3:4.
• Codominance: Both alleles expressed, doesn't change the 9:3:3:1 to 9:3:4.
• Epigenesis: Deals with developmental processes, not genetic ratios.
• Epistasis: Interaction between genes where one gene modifies the phenotypic ratio of another. A 9:3:4 ratio is a type of epistatic interaction (recessive epistasis, where one recessive allele masks the expression of another gene).

1. Analyze the ratio change: The regular dihybrid ratio (9:3:3:1) is modified to 9:3:4, which fits the pattern of epistasis (specifically recessive epistasis here, where the 3:1 parts combine due to epistatic interaction).

Answer:

D. Epistasis