Final answer:
To distinguish genes on different chromosomes from those far apart on the same chromosome with 50% recombination, geneticists use linkage mapping and observe the recombinant offspring frequency, which reflects genetic distance.
Step-by-step explanation:
To distinguish between genes on different chromosomes and genes located far apart on the same chromosome, especially if genes exhibit 50% recombination, we look to the process of linkage mapping. Genes on separate, nonhomologous chromosomes assort independently during meiosis, giving them a 50% chance of ending up in different gametes, which is referred to as independent assortment.
Conversely, genes that are located on the same chromosome tend to be inherited together unless they are so far apart that crossovers during meiosis occur frequently enough to mimic the pattern of independent assortment.
The frequency of recombinant offspring—those with nonparental genotypes—serves as a measure of the genetic distance between two genes on the same chromosome. Linkage maps are created by calculating the recombination frequencies, with a higher frequency suggesting greater distance between genes.
Crossovers happening less than 50% of the time indicate that the genes are on the same chromosome and likely linked, while a crossover frequency near 50% indicates either the genes are far apart on the same chromosome or on different chromosomes.