Can you please explain me what is linkage in detail

Linkage in simple words means that how close two genes are on the chromosome. If two genes are very close it means they are linked so these two genes will be inherited together and thus chances of recombination decrease.
You can say linkage is inversely proportional to recombination between two genes.

Take the following two cases please.

In first figure the two genes are farther apart.
Since Gene 1 and Gene 2 are far apart, it is likely that a recombination event will happen between them. When this happens, the gametes end up with new allele combinations that were not present in the parent. That is, 1-B with 2-A, and 1-A with 2-B.




Gene 3 and Gene 4 ( see below figure) also come in two alleles each (A and B). But because these genes sit much closer together, it is less likely that a recombination event will happen between them. Most of the time, 3-A and 4-A will stay together, and 3-B and 4-B will stay together. Genes 3 and 4 are linked.

Approved