How would the results vary in cross (a) of Problem 32 if genes A and B were linked with no crossing over between them? How would the results of cross (a) vary if genes A and B were linked and 20 map units (mu) apart?

Key Concepts

Gene Linkage

Gene linkage refers to the tendency of genes located close to each other on the same chromosome to be inherited together during meiosis. When genes are linked, they do not assort independently, which can affect the ratios of offspring phenotypes in genetic crosses. Understanding linkage is crucial for predicting the outcomes of crosses involving multiple genes.

Crossing Over

Crossing over is a process that occurs during meiosis where homologous chromosomes exchange segments of genetic material. This recombination can create new allele combinations, affecting the genetic variation in offspring. If genes A and B are linked with no crossing over, the parental combinations will be preserved, leading to fewer recombinant types in the offspring.

Map Units and Genetic Distance

Map units, or centimorgans (cM), measure the distance between genes on a chromosome based on the frequency of recombination events. One map unit corresponds to a 1% chance of recombination occurring between two genes. If genes A and B are 20 map units apart, there is a 20% chance of recombination, which will increase the proportion of recombinant offspring compared to genes that are tightly linked.