Strength of linkage is related inversely to distance between
Genes
Morgan found that when genes are found on the same chromosome, some were very tightly linked genes while others were loosely linked. Tightly linked genes usually do not get separated during crossing over. Linked genes sit close together on a chromosome, making them likely to be inherited together. Genes on separate chromosomes are never linked. But not all genes on a chromosome are linked. Genes that are farther away from each other are more likely to be separated during a process called homologous recombination. So strength of linkage depends on the distnce between genes.