Can you tell me about genetic linkage/mapping question?

Linkage = correlatio: Genetic mapping refers 2 locating genes on their chromosomes. The reason why this is of scientific interest is because certain genetic traits or characteristics seem to be correlated with others & w/ certain DNA segments which can be tested. E.g., the gene (if defective) that causes color blindness is often seen in cystic fibrosis, & so can be checked by CFTR gene analysis. Any specific question?