In Drosophila, a female fly is heterozygous for three mutations, Bar eyes (B), miniature wings (m), and ebony body (e). Note that Bar is a dominant mutation. The fly is crossed to a male with normal eyes, miniature wings, and ebony body. The results of the cross are as follows. 111 miniature 101 Bar, ebony 29 wild type 31 Bar, miniature, ebony 117 Bar 35 ebony 26 Bar, miniature 115 miniature, ebony Interpret the results of this cross. If you conclude that linkage is involved between any of the genes, determine the map distance(s) between them.

Key Concepts

Genetic Linkage

Genetic linkage refers to the tendency of genes located close to each other on a chromosome to be inherited together during meiosis. This phenomenon occurs because linked genes are less likely to be separated by recombination events. Understanding linkage is crucial for interpreting genetic crosses, as it can affect the expected ratios of offspring phenotypes.

Map Distance

Map distance is a measure of the relative distance between genes on a chromosome, typically expressed in centimorgans (cM). It is calculated based on the frequency of recombination events between genes during meiosis. A higher map distance indicates a greater likelihood of recombination, suggesting that the genes are further apart on the chromosome.

Phenotypic Ratios

Phenotypic ratios represent the relative frequencies of different observable traits in the offspring resulting from a genetic cross. These ratios can provide insights into the inheritance patterns of traits, including dominance, recessiveness, and linkage. Analyzing the observed phenotypic ratios helps in determining whether the genes assort independently or are linked.