What genotypes are responsible for red eyes in fruit flies?

The red eye color in fruit flies, specifically Drosophila melanogaster, is primarily influenced by the alleles of the white gene (w). The gene has two primary alleles: the wild type allele (w+) is responsible for the normal red eye color, while the mutant allele (w) causes white eyes.

Individuals with the genotype w+/w+ have two copies of the wild type allele, ensuring a strong expression of red eye color. Those with the genotype w+/w will still produce red eyes since the presence of just one wild type allele is sufficient to express the red phenotype due to the dominance of w+ over w. Therefore, the w+/w genotype also leads to red eyes but has one recessive allele that does not express.

In comparison, the w/w genotype results in white eyes, as there are no wild type alleles to produce the red color. Those with the genotype w/w+ could also possess red eyes since w+ is dominant, leading to some individuals still expressing the red phenotype. However, since the question specifically asks about genotypes that result in red eyes, w+/w (one wild type allele for red eyes) is the direct response needed.

Thus, the w+/w genotype can