Four eye-color mutants in Drosophila—apricot, brown, carnation, and purple—are inherited as recessive traits. Red is the dominant wild-type color of fruit-fly eyes. Eight crosses (A through H) are made between parents from pure-breeding lines.

Predict F₂ phenotype ratios of crosses A, B, D, and G. <>

Key Concepts

Mendelian Inheritance

Mendelian inheritance refers to the principles of heredity established by Gregor Mendel, which include the concepts of dominant and recessive traits. In this context, the eye color traits in Drosophila demonstrate how alleles interact, with red being the dominant trait and the mutants (apricot, brown, carnation, and purple) being recessive. Understanding these principles is essential for predicting the phenotypic ratios in offspring from specific crosses.

Phenotypic Ratios

Phenotypic ratios represent the relative frequencies of different phenotypes in the offspring resulting from genetic crosses. In this case, the F₂ generation's phenotypic ratios can be predicted based on the genotypes of the parents and the inheritance patterns of the eye color traits. Analyzing these ratios helps in understanding the distribution of traits in the population.

Pure-Breeding Lines

Pure-breeding lines consist of organisms that consistently produce offspring with the same phenotype when self-fertilized or crossed with other individuals of the same line. In the context of the question, the use of pure-breeding lines for the eye color mutants allows for clear predictions of the F₂ generation's phenotypes, as these lines are homozygous for their respective traits, simplifying the genetic analysis.