Final answer:
Linked genes are on the same chromosome and tend to be inherited together, but crossing-over can separate them, affecting linkage based on the genes' proximity.
Step-by-step explanation:
Linkage and Crossing-Over in Genetics
Genes that are located on the same chromosome are referred to as linked genes. This physical proximity often results in the alleles for these genes being segregated together during meiosis, which is known as genetic linkage. The process of crossing-over, however, can affect this linkage. During meiosis I, crossing-over can occur when homologous chromosomes exchange genetic material. This recombination can separate alleles that were previously linked, leading to genetic variation.
How close together genes are on a chromosome greatly influences the likelihood of crossing-over separating their alleles. The closer the genes are located to each other, the less likely it is for crossing-over to occur between them, resulting in alleles that remain linked. Conversely, as the distance between two genes increases, the frequency of crossing-over also increases, and the genes may behave as if they are unlinked. Geneticists use the proportion of recombinant (nonparental) gametes—a result of crossing-over—to construct linkage maps. These maps depict the relative positions of genes on a chromosome, effectively representing the genetic distance between them.
In conclusion, while linked genes on the same chromosome tend to be inherited together, crossing-over during meiosis can separate alleles of these genes—especially when they are farther apart—leading to greater genetic diversity. The frequency of crossing-over is therefore an essential tool for geneticists when mapping linkage and gauging the distance between genes on a chromosome.