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 recombination frequencies between the adjacent genes.

Key Concepts

Recombination Frequency

Recombination frequency is a measure of the likelihood that two genes will be separated during meiosis due to crossing over. It is calculated by dividing the number of recombinant offspring by the total number of offspring, then multiplying by 100 to express it as a percentage. This frequency helps in determining the genetic distance between genes on a chromosome.

Trihybrid Cross

A trihybrid cross involves organisms that are heterozygous for three different traits. In this case, the wild-type soybean plant carries dominant alleles for traits such as leaf color, seed shape, and plant height, while the pure-breeding plant has recessive alleles. Analyzing the offspring from such a cross allows researchers to study the inheritance patterns and interactions of multiple genes.

Three-Point Test Cross

A three-point test cross is a genetic cross used to determine the arrangement of three linked genes on a chromosome. By crossing a trihybrid organism with a homozygous recessive organism, the resulting offspring's phenotypes can reveal the linkage and order of the genes. The phenotypic ratios observed in the offspring help calculate recombination frequencies and infer genetic maps.