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G. W. Montgomery, J. A. Sise, P. J. Greenwood, and J. S. Fleming

ABSTRACT

A cDNA probe for the β subunit of bovine FSH (FSH-β) detects multiple restriction fragment length polymorphisms (RFLPs) in sheep genomic DNA consistent with an insertion/deletion polymorphism around the FSH-β locus. The presence of the insertion/deletion was confirmed by screening over 100 individuals with two restriction enzymes detecting RFLPs. All individuals showed the same patterns of fragments with both enzymes. A partial restriction map of the FSH-β gene in sheep suggests that the insertion/deletion is approximately 2 kb in size and located downstream from the third exon. Individual DNA samples were analysed from two flocks where the Booroola F gene is known to be segregating. Individuals that were heterozygous for the F gene were shown to be homozygous for one or other of the two alleles. Genetic recombination between the FSH-β locus and the F gene was observed in four pedigrees and there was no evidence that the insertion/deletion is closely linked genetically to the Booroola F gene. A major gene transcript of 2·2–2·3 kb was detected on Northern blots of sheep RNA. Neither the insertion/deletion polymorphism nor the presence of the F gene appeared to influence the size of the FSH-β gene transcript.

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G W Montgomery, M L Tate, H M Henry, J M Penty, and R M Rohan

ABSTRACT

Restriction fragment length polymorphisms were identified in sheep and deer using ovine cDNA probes for the FSH receptor (FSHR) and the LH receptor (LHCGR). FSHR and LHCGR were closely linked in sheep with no recombinants and neither receptor was linked to the Booroola fecundity gene (FecB). Both receptors were also closely linked in deer at a map distance of 3·3 cM. Linkage between the receptor genes assigns FSHR to sheep chromosome 3. Sequence analysis showed that the mammalian LHCGRs and FSHRs are more similar to each other than to mammalian TSH receptor (TSHR). Taken together, these data suggest that TSHR and the LHCGR/FSHR arose from a common ancestral gene by a process of chromosomal duplication. Subsequent duplication of the region containing the LH/FSH receptor and functional divergence could have given rise to the two gonadotrophin receptors present in mammals today.