Abundant (A)n.(T)n mononucleotide repeats in the pig genome: linkage mapping of the porcine APOB, FSA, ALOX12, PEPN and RLN loci.

A computer analysis revealed that the mononucleotide repeat (A)n.(T)n is about five times as common as (CA)n.(GT)n repeats in the porcine genome, with frequency estimates of one every 7kb and 30kb, respectively. Seven mononucleotide repeats with n = 12-25 located close to coding sequences were analysed for polymorphism using polymerase chain reaction (PCR) amplification and polyacrylamide gel electrophoresis. All loci were variable with 3-6 alleles and heterozygosities of 0.26-0.69 based on investigation of 10 unrelated pigs (two wild boars and eight domestic sows). Repeat length correlated with degree of polymorphism. A comparison with (CA)n.(GT)n polymorphisms suggested that the number of repeat units rather than the total length of the repeat region is the common denominator that governs polymorphism at both mono- and dinucleotide repeat loci. (A)n.(T)n polymorphisms allowed linkage mapping of relaxin to chromosome 1, apolipoprotein B to chromosome 3, aminopeptidase N to chromosome 7, arachidonate 12-lipoxygenase to chromosome 12, and follistatin to chromosome 16. The rich abundance of potentially informative (A)n.(T)n repeats will increase the chances of finding a PCR-based marker near any DNA sequence of interest.