What is the dominant phenotype in Drosophila regarding body color?

• A. Yellow body
• B. Dark body
• C. Recessive trait
• D. White body

Answer: (B)

In Drosophila melanogaster, also known as the fruit fly, body color is a trait that is determined by specific alleles. The dominant phenotype for body color in Drosophila is indeed the dark body color, which is usually represented by the allele "B". This dominance indicates that when the genotype includes at least one allele for a dark body, the phenotype expressed will be dark.

In contrast, the other options reflect colors that are either recessive or are simply not the dominant phenotype. The yellow body trait is recessive, and only individuals with two recessive alleles for this trait will exhibit a yellow body color. The white body option is associated with a different gene and is also a recessive trait. Such traits can only manifest in the absence of the dominant allele, explaining why dark body color prevails.

Understanding the dominance of certain traits helps in predicting the phenotypes of offspring when crossing Drosophila specimens with known genotypes. Thus, the dark body color represents the dominant phenotype in these flies, establishing a clear expectation for observable traits in these genetic studies.