Genetic marker assisted selection in cattle: leptin gene locus and its polymorphism

We studied the polymorphism of types RFLP-Sau 3AI, RFLP-Mbo I and RFLP-Bsa AI at the leptin gene locus, in two improved genuine breeds: B l at Romaneasc and Brun de Maramure . The comparative use of different DNA separation, amplification and genotypization protocols allowed us to select the most suitable techniques for polymorphism studies, taking into consideration the accuracy of the obtained results, reproducibility, costs and equipments. The DNA obtained using automatic MagnaPure LC kit, was of a very good quality, and did not exhibit traces of degradation. It iwas free of RNA and protein contamination. The posibility of using refrigerated and old blood advantages the use of this method. We recommend the use of protocols described by Liefers et al (2002) and Lien et al (1997) for the study of polymorphism of the leptin gene and genotypization at this locus, as we demonstrated that they could produce better results, as compared to those obtained when the protocol of Pomp et al (1997) was used. In the studied B l at Romaneasc and Brun de Maramure populations, the allele A had a higher frequency at the leptin gene locus, as compared to allele B. Analyzing the frequencies of the genotypes in B l at Romaneasc individuals, we noticed that the AA homozygous genotype represents 60%, AB heterozygous genotype 36% and BB homozygous genotype the smallest share, 4%,respectively of the total genotypes. Frequencies were similar for Brun de Maramure , with the differencethat BB genotype was absent.