Study On The Relationship Between Goat Agouti Gene And Color Phenotype And Its Variation In Goat Populations

On the basis of sequences from GenBank,part of exonl and intronl of goat Agouti gene fragments was amplified.The fragment of intronl was joined with the fragment we had got before which had been handed out to GenBank,the Accession Number was EF587236.Two new point mutations were found in this fragment,and the only mutation in coding region of goat Agouti gene was analyzed again,so we named these 3 mutations were named as follow:399C＞T,128delT and 5701G＞T.And the mutation 5701G＞T lead to the amino acid substitution ofG(Gly)for V(Val)at the position 125.A total of 545 individuals from nine Chinese indigenous goat breeds were analyzed for 5701G＞T by PCR-RFLP in order to investigate its genetic effect and diversity.Two alleles of T and G,three genotypes of TT,TG and GG were detected.The allele T was superiority gene in most goat breeds, together analyses with the phenotype of coat color,and then we postulated that T was associated with black phenotype or linked with the site controlling the black coat color in goat.The results also suggested that the 5701G＞T site performed lower genetic diversity in goat breeds with black coat color in China.The genetic differentiation among 9 goat populations was 0.2615.The clustering of populations based on 5701G＞T site was basically consistent with the variation of coat color.There is a tendency that goat breeds with higher T frequency have lower adult body weight.It could be inferred that the 5701G＞T in Agouti gene exon 4 might be related with the growth development of goat.The genetic diversity of 128delT del in Chinese indigenous goat breeds was analyzed,as well as the relationship between the genotype and the coat color phenotype by PCR-RFLP.Two alleles of A(del) and B(non-del),three genotypes of AA,AB and BB were detected.The genotype AA was superior in brown coat color goat breeds(78.69%);genotype AB existed mainly in white coat color goat breeds (76.14%)and the goat breeds with black coat color have BB genotype mostly(75.86%),so we deduced that the 128delT del might have the effect on the pigment synthesis of goat.The expected heterozygosity, the gene flow and the mean coefficient of gene differentiation of 128delT del among ten goat breeds were 0.4718,0.3190 and 0.4393 respectively.The results indicated that most goat breeds investigated here were poor in genetic diversity at 128delT del.