A PHYSICALLY ANCHORED LINKAGE MAP OF PIG CHROMOSOME-1 UNCOVERS SEX-SPECIFIC AND POSITION-SPECIFIC RECOMBINATION RATES

A linkage map of pig chromosome 1 (SSC1) has been constructed using 15 polymorphic markers. Eleven markers constitute PCR based microsatelli tes (three associated with coding sequences), six markers have also be en mapped by in situ hybridization, and homologues to four of the mark ers have been mapped in human. The physical assignments show that almo st the entire SSC1 is covered by the linkage map, which measures 164 c M (sex-averaged). In a large region on the q arm, representing about 4 0% of the chromosome, there is a significant excess of male recombinat ion. In contrast, there is a significantly higher recombination rate i n females in both terminal regions. In the penultimate marker interval s on the q arm as well as the p arm, females show a fivefold excess of recombination compared to males. The rate of genetic recombination in relation to the physical DNA content is 1 cM per 2-4 Mb over at least 80% of the chromosome. In the terminal part of the q arm, however, th ere is a tremendous increase ire the recombination rate, with 1 cM equ aling about 0.4 Mb. Two homologous chromosome segments in human could be detected, ESR-CGA on human chromosome 6 (HSA6) and IFNA-RLN-GRP78 o n human chromosome 9 (HSA9). Since the porcine blood group locus EAA i s located close to (or possibly within) the latter conserved segment a nd the suggested human counterpart, the ABO system, is similarly close to the segment on HSA9, our data provide indirect evidence that these blood group systems are homologous. (C) 1991 Academic Press, Inc.