Genetic Variations Of Yaks In Gansu:Inferred From Their Milk Protein Polymorphisms

To investigate the genetic variability within populations and genetic differentiation between populations of yaks, milk protein polymorphisms in yaks (Bos grunniens). cattle (Bos taurus) and their F I hybrids were examined. Simultaneous phenotyping by conventional discontinuous polyacrylamide gel electrophoresis detected two genotypes (BB and AB) f a -lactalbumin, six genotypes (AA, AB, AE. BB, BE and EE) of fi -lactoglobulin, and two genotypes (AA and AB) of fi -casein. The degree of genetic variability within populations estimated by Nei's average heterozygosity for these three milk protein loci of a -La, 6 -Lg and 6 -Cn was relatively lower in yaks (0-10.62%) than that in cattle (26.61%) and their Fl hybrids (19.65%). The average genetic diversities within yak populations (Hs) and in the total yak population (HT) were 4.8% and 5.2% respectively. The average genetic diversity between yak popualtions (DST) was 0.44% and the relative magnitude of genetic differentiation among yak populations was 8.4%. The results showed that the genetic variations both within and between yak populations were very limited. Therefore, it was supposed that the close species, such as Bos taurus, should be used to richen the genetic diversity of yaks.