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Animal, Dairy, and Veterinary Sciences


The purpose of this experiment was to determine if the estrogen receptor gene (ESR) could be used as a genetic marker for litter size in sheep. The estrogen receptor gene was chosen because it has been successfully used as a genetic marker for litter size in swine. In this study, DNA dilutions from two experimental flocks, totaling approximately 200 animals, were used. Amplification of exon 1/intron 1 of the ESR gene was performed using PCR. Initial results indicated a polymorphism in the gene when cut with the restriction enzyme Ava ll. It appeared that the gene contained a deletion with the high-producing animals being heterozygous and the low-producing animals being homozygous for the deletion-containing fragment. However, when the gene was amplified with different primers and the protocol was changed to a hot start PCR, the initial difference was lost and all animals showed identical bands regardless of average litter size. A final screen of both flocks revealed no difference in the Ava ll restriction pattern of exon 1 in ESR. Thus, a genetic marker for litter size in sheep could not be identified in the ESR gene using the current protocol.

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