A wild-type trihybrid soybean plant is crossed to a pure-breeding soybean plant with the recessive phenotypes pale leaf (l), oval seed (r), and short height (t). The results of the three-point test cross are shown below. Traits not listed are wild type. Phenotype Number Pale   648 Pale, oval     64 Pale, short     10 Pale, oval, short   102 Oval       6 Oval, short   618 Short     84 Wild type     98 1630 Calculate the interference value for these data.

Key Concepts

Trihybrid Cross

A trihybrid cross involves three pairs of contrasting traits, allowing the study of inheritance patterns for multiple genes simultaneously. In this case, the traits are leaf color, seed shape, and plant height. Understanding how these traits segregate and assort independently is crucial for analyzing the offspring's phenotypes and calculating genetic ratios.

Three-Point Test Cross

A three-point test cross is a genetic cross used to determine the arrangement of genes on a chromosome and the distances between them. By crossing a trihybrid organism with a homozygous recessive organism, the resulting offspring's phenotypes reveal information about gene linkage and recombination frequencies, which are essential for calculating genetic interference.

Genetic Interference

Genetic interference refers to the phenomenon where the occurrence of one crossover event in a region of a chromosome affects the likelihood of another crossover occurring nearby. It is quantified using the interference value, which can be calculated from the observed and expected double crossover frequencies. Understanding interference helps in mapping genes and understanding genetic linkage.