The estrogen receptor locus is associated with a major gene influencing litter size in pigs.

Identification of individual major genes affecting quantitative traits in livestock species has been limited to date. By using a candidate gene approach and a divergent breed cross involving the Chinese Meishan pig, we have shown that a specific allele of the estrogen receptor (ER) locus is associated with increased litter size. Female pigs from synthetic lines with a 50% Meishan background that were homozygous for this beneficial allele produced 2.3 more pigs in first parities and 1.5 more pigs averaged over all parities than females from the same synthetic lines and homozygous for the undesirable allele. This beneficial ER allele was also found in pigs with Large White breed ancestory. Analysis of females with Large White breed background showed an advantage for females homozygous for the beneficial allele as compared to females homozygous for the other allele of more than 1 total pig born. Analyses of growth performance test records detected no significant unfavorable associations of the beneficial allele with growth and developmental traits. Mapping of the ER gene demonstrated that the closest known genes or markers were 3 centimorgans from ER. To our knowledge, one of these, superoxide dismutase gene (SOD2), was mapped for the first time in the pig. Analysis of ER and these linked markers indicated that ER is the best predictor of litter size differences. Introgression of the beneficial allele into commercial pig breeding lines, in which the allele was not present, and marker-assisted selection for the beneficial allele in lines with Meishan and Large White background have begun.

Photocleavable biotin derivatives: a versatile approach for the isolation of biomolecules.

While the strong biotin-avidin interaction has been widely used for the detection of biomolecules, its irreversibility complicates their isolation. We report the synthesis of a photocleavable biotin derivative (PCB) which eliminates many limitations of existing methods. This reagent contains a biotin moiety linked through a spacer arm to a photocleavable moiety, which reacts selectively with primary amino groups on any substrate. In experiments using [leucine]-enkephalin as a model substrate, we show that PCB retains its high affinity toward avidin/streptavidin and allows rapid (< 5 min) and efficient (> 99%) photorelease of the substrate in a completely unaltered form. Photocleavable biotins should be useful in numerous applications involving the isolation of proteins, nucleic acids, lipids, and cells.