Linkage is the close association of genes or other DNA sequences on the same chromosome. The closer two genes are to each other on the chromosome, the greater the probability that they will be inherited together.
Linkage is referring to the close co-location of genes or of DNA variations to each other on the chromosomes. And these co-localizations are close enough that one can use genetic tools to find them being transmitted within families together. And the closer genes are to each other on a chromosome, the better chance you have to detect this linkage, because they are then more likely to be transmitted from grandparents, to parents, to children together, because there's less likely to be recombinations at meiosis between these genes. And so two genes that tend to be transmitted together we say are linked to each other.Joan E. Bailey-Wilson, Ph.D.