Question

Fruit colour in squash is an example of

• A. recessive epistasis
• B. dominant epistasis
• C. complementary genes
• D. inhibitory genes.

Answer 1

The Correct Option is B

To understand the answer to the question, "Fruit colour in squash is an example of," we need to explore the genetic concept of epistasis and its types. Epistasis refers to the interaction of genes wherein the effect of one gene is modified by one or several other genes, which can influence phenotypic outcomes.

In this particular case, the fruit color in squash is a well-known example of dominant epistasis. This type of epistasis occurs when the presence of a dominant allele of one gene masks the effects of alleles of another gene.

1. Dominant Epistasis Example in Squash:
   • Consider a gene 'A' which controls yellow vs. green fruit color, where 'A' (yellow) is dominant over 'a' (green).
   • There is another gene 'B' which controls whether the fruit is white or colored, where 'B' (white) is dominant over 'b' (color is expressed).
   • In squash, the presence of the dominant 'B' allele leads to white fruits, irrespective of the alleles present at the 'A' locus.
   • Thus, genotypes 'BB', 'Bb' will produce white fruits, masking the effect of 'A' alleles which would produce yellow or green fruits only if 'bb' is present.

Considering the options:

• Recessive Epistasis: Involves a recessive gene masking the effect of another gene, not applicable here as dominance is involved.
• Complementary Genes: Two different gene pairs are required for a single phenotype, not relevant as single-gene interactions describe the squash scenario.
• Inhibitory Genes: Generally imply suppression of gene expression, but not through dominant interactions as seen in squash.
• Dominant Epistasis: Correct explanation for the gene interaction seen in squash where one dominant gene masks the output of another.

Therefore, the correct answer is "dominant epistasis".