Detection of A1 and A2 Alleles at Beta-casein Locus in Bargur and Umblachery (Indian Zebu) Cattle Breeds by Allele-specific PCR

Abstract

Background: Many genetic variants of beta-casein in different breeds of cattle have been reported. The A1 and A2 are the most common variants. The breeds of Zebu cattle have high frequency of A2 allele or monomorphic for A2 allele. The current study aimed to screen Indian Zebu cattle breeds, Bargur and Umblachery, for A1 and A2 alleles at beta-casein locus.Methods: A total of 48 Bargur and 42 Umblachery cattle were genotyped for β-casein (CSN2) gene using allele-specific PCR. The gene and genotype frequencies were estimated. The theoretical heterozygosity (Heexp), experimental heterozygosity (Heobs), polymorphism information content (PIC), expected homozygosity (E), effective number of alleles (ENA) and level of possible variability realization (V%) were calculated.Result: The investigation revealed the presence of both A1 and A2 alleles at beta-casein locus in both Bargur and Umblachery cattle breeds. The A1A1 genotype was not observed in both the breeds. The frequencies of A1A2 and A2A2 genotypes were 0.125 and 0.875 respectively in Bargur and 0.050 and 0.950 respectively in Umblachery breed. The study indicated the predominance of A2 variant in both the breeds. The frequencies of A1 and A2 alleles were 0.063 and 0.937 respectively in Bargur and 0.02 and 0.98 respectively in Umblachery breed. The values of experimental heterozygosity (Heobs), theoretical heterozygosity (Heexp), polymorphism information content (PIC), expected homozygosity (E), effective number of alleles (ENA), level of possible variability realization (V%) were 0.125, 0.1163, 0.1095,0.8837, 1.131 and 11.88 respectively in Bargur breed. These values were 0.048, 0.0468, 0.0458, 0.9532, 1.049 and 4.79 respectively in Umblachery population. The observed heterozygosity and PIC values revealed the existence of very low genetic variability in the tested populations. The present work will be a contribution to the study on beta-casein locus in Indian zebu cattle.