Final answer:
Alleles for each gene are found at a specific locus on homologous chromosomes. Crossing-over during meiosis can shuffle these alleles. Linked genes on a chromosome tend to be inherited together, while genetic linkage maps show gene locations.
Step-by-step explanation:
The alleles for each gene are located at the same place, or locus, on each molecule of homologous chromosomes. These chromosomes carry the same genes in the same order, but the alleles may vary between the pair received from each parent. During the process of meiosis, specifically in meiosis I, homologous chromosomes replicate and pair up in a process called synapsis. It is during this paired up stage that crossing-over may occur, leading to genetic recombination where maternal and paternal alleles get mixed on the same chromosome. This shuffling of alleles is an important source of genetic diversity. Genes that are physically close to one another on the same chromosome are considered linked genes because they are more likely to be inherited together. Geneticists use crossover frequency to construct linkage maps that depict the location of genes on chromosomes. These maps can illustrate how likely it is for alleles of two linked genes to be separated by recombination and inherited separately.