作者单位:Univ Missouri, Dept Anim Sci, Columbia, MO USA[1]Univ Minnesota, Dept Genet Cell Biol & Dev, Minneapolis, MN USA[2]Univ Utah, Dept Biochem, Salt Lake City, UT USA[3]Univ Utah, Dept Biol, Salt Lake City, UT 84112 USA[4]Univ Calif Davis, Dept Anim Sci, Davis, CA 95616 USA[5]