Genetic Polymorphism of Whey Protein Genes β-LG and α-LA in Three Egyptian Sheep Breeds

Abstract

The major whey proteins, β-lactoglobulin (β-LG) and α-lactalbumin (α-LA), are strongly correlated with the nutritional value and the functional properties of milk whey. Ovine whey has a unique protein composition compared to that of bovine whey and it is especially rich in proteins. Genetic polymorphism of β-LG using PCR-RFLP and α-LA using PCR-SSCP was analyzed in three native Egyptian sheep breeds named Barki, Rahmani and Ossimi. Digestion of resulting amplified fragments of β-LG (452-bp) with RsaI endonuclease differentiated between three different genotypes AA (69.77%), AB (26.74%) and BB (3.49%). The results showed that A allele was present in the Egyptian sheep breeds with a frequency (83.14%) higher than B allele (16.86%). A & B alleles appeared at frequencies 70.4 % & 29.6%, 95.0% & 5.0% and 82.8% & 17.2% in Barki, Rahmani and
Ossimi, respectively SSCP results of the α-LA amplified fragments (166-bp) showed that the three native Egyptian sheep breeds possess two different patterns related to the difference in nucleotide sequences with frequencies 88.1% and 11.9%. The frequencies of pattern 1 ranged from 81.48% in Barki to 89.66% in Ossimi and 92.86% in Rahmani breeds whereas the pattern 2 was present at frequencies 18.52%, 7.14% and 10.34% in Barki, Rahmani and Ossimi breeds, respectively