In Drosophila genetics, which trait is dominant: red eyes or white eyes?

In Drosophila, or fruit flies, the trait for red eyes is dominant over the trait for white eyes. This is a classic example of Mendelian inheritance where one allele can mask the presence of another. In these flies, the gene responsible for eye color has two alleles: one allele for red eyes, which is dominant, and another allele for white eyes, which is recessive.

When both alleles are present in an individual (heterozygous condition), the dominant red allele expresses itself, resulting in red-eyed flies. In contrast, the flies will only exhibit white eyes if they are homozygous for the white allele, meaning they possess two copies of the recessive allele. This demonstrates the fundamental principle of dominance in genetics where the dominant allele's trait is observable in the phenotype, while the recessive allele's trait is masked when paired with the dominant allele.

Understanding the dominance relationship between these traits is crucial for predicting the phenotypic outcomes in Drosophila and applying this knowledge to more complex genetic crosses.