Genes A, B, C, D, and E are linked on a chromosome and occur in the order given.

The test cross  indicates the genes recombine with a frequency of 28%. If 1000 progeny are produced by this test cross, determine the number of progeny in each outcome class.

Key Concepts

Genetic Linkage

Genetic linkage refers to the tendency of genes located close to each other on the same chromosome to be inherited together during meiosis. This phenomenon affects the assortment of alleles and can influence the frequency of recombination events. Understanding linkage is crucial for predicting the outcomes of genetic crosses, especially when calculating progeny ratios.

Recombination Frequency

Recombination frequency is a measure of the likelihood that two genes will be separated during meiosis due to crossing over. It is expressed as a percentage, with higher values indicating greater distances between genes on a chromosome. In this scenario, a recombination frequency of 28% suggests that 28% of the gametes will show a combination of alleles different from the parental types.

Test Cross

A test cross involves breeding an individual with a dominant phenotype but unknown genotype with a homozygous recessive individual. This method helps determine the genotype of the dominant individual based on the phenotypic ratios of the offspring. In the context of the question, the test cross provides essential data on the recombination frequency, which is used to calculate the expected progeny classes.