In Drosophila genetics, what do white eyes signify?

• A. A dominant trait
• B. A recessive trait
• C. Insufficient dominant alleles
• D. A lethal mutation

Answer: (B)

In Drosophila genetics, the presence of white eyes signifies a recessive trait. Specifically, the gene responsible for eye color in fruit flies has a common variant that produces red eyes, which is the dominant phenotype. In contrast, individuals carrying the recessive allele for the white-eye trait do not have the sufficient expression of the dominant allele, resulting in the white-eye phenotype.

This understanding stems from classic Mendelian genetics, where traits are classified as dominant or recessive based on their expression in heterozygous individuals. Since the white-eye trait only appears in flies that are homozygous for the recessive allele (where two copies of the recessive allele are present), it illustrates the fundamental concept of how recessive traits are passed on and expressed in progeny.

The other options don't apply because a dominant trait would result in red eyes if any dominant allele is present, insufficient dominant alleles does not provide correct terminology in this context, and a lethal mutation would not survive to produce offspring with white eyes since those mutations typically result in organismal death before reproduction.