Linkage analysis has been made easier with the use of restriction fragment length polymorphisms, or RFLPs. RFLPs are different sized fragments of DNA created by polymorphisms in the recognition sites of restriction endonucleases. However, neither of these two linkages has been confirmed. While linkage refers to cosegregation of disease and a marker allele within families, association refers to population differences. Association studies are less complicated than other forms of genetic analysis because DNA only needs to be obtained from affected individuals, and not from a large number of family members.
Association studies are very specific.
If an association is present, the disease-influencing gene will be found very quickly. However for this to occur, the candidate gene that is chosen must be very nearly exactly correct. If variation at a locus affects the phenotype under study, an association study will only be able to detect that effect if the variant allele is in strong linkage disequilibrium with the marker alleles being tested.