Genetic Polymorphisms of Milk Genes (β-Lactoglobulin and κ-Casien) in Palestinian Awwasi Sheep Breeds

Abstract

Milk and dairy products from small ruminant species represent a significant part of the agricultural economy worldwide especially in marginal areas. Evidences showed that there is a strong association between milk protein polymorphisms and milk yield. So, it is necessary to make available in-depth information regarding genetic polymorphisms of milk proteins in sheep breeds in Palestine with consideration of the great genetic biodiversity of sheep breeds.This study was conducted to assess the polymorphisms of κ-casein (κ-CN) and β-lactoglobulin (β-LG) genes of the main breeds of Palestinian Awassi sheep (local and improved Awassi) and their effect on milk quality. DNA was extracted from 54 sheep (23-local Awassi and 31- improved Awassi). The κ-CN and ß-LG were amplified using Polymerase Chain Reaction (PCR). Restriction Fragment Length Polymorphism (RFLP) technique was used to determine variations at the ß-LG loci, while for K-CN direct sequencing was performedby Sanger sequencing. The amplified products for ß-LG and K-CN genes had the sizes of 471 bp and 670bp, respectively. Digestion of β-lactoglobulin gene using RsaIrestriction enzyme revealed the presence of three genotypes (AA, AB, and BB). The results of ß-LG the sequence analysis of exon 2 revealed a point mutation (C→ T), a single base substitution T instead of C of the (X12817.1:c.112 T>C) locus in both local and improved Awassi which is xiv responsible for the amino acid exchange of histidine to tyrosine. The results of κ-CN sequence analysis showed the presence of three different patterns; CC, TC and TT. Sanger sequencing results revealed a single base pairsubstitution (C→ T) in codon no 56 of exon three, this mutation is asynonymous variant. Statistical analysis showed that a significant effects of β-LG genotypes on fat contentand densityof milk in local but not improved Awassi;whereas significant effect of certain κ- CN genotype onSNF of milkin local Awassi only, while no effects of these genotypes on milk quality were significantly detected in improved Awassi.