Genotype and promoter sequence characteristics of β-lactoglobulin in Sanhe cow
[Objective]The genotype of β-lactoglobulin(β-Lg)in Sanhe cow was analyzed,and the relationship between its promoter sequence and milk content was explored.[Method]Polyacrylamide gel electrophoresis(PAGE)was used to detect the genetic variants of β-Lg in milk and their relative expression levels,and the sequence differences of different genetic variants were compared by PCR amplification and sequencing.[Result]There were three genotypes of AA,AB and BB in β-Lg in whey of Sanhe cows(n=62),and the frequencies were 0.290,0.403 and 0.307,respectively.The frequencies of A and B al-leles were similar.The partial sequences of 37 homozygous β-Lg promoters were amplified by PCR(636 bp)and sequenced,and compared with the bovine β-Lg gene sequence(GenBank accession number:U31361.1).A total of 6 mutation sites were detected,of which the-430,-362,-216 and-204 sites were basically allele-specific.A HPLC method for the determina-tion of β-Lg in Sanhe cow milk was established.It was found that the content of β-Lg in AA type was significantly higher than that in AB type(P＜0.01),but there was no significant difference among AA,AB and BB types.[Conclusion]The allele frequencies of β-LgA and B in Sanhe cow were similar,and the promoter-430,-362,-216 and-204 loci have allele specificity and may affect allele expression.
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