ABSTRACT. The aim of the study was to detect polymorphisms in the leptin gene and to determine the association of these polymorphisms with growth and carcass traits in Nellore cattle. The single nucleotide polymorphisms (SNPs) -1457 (AJ571671:g.-1457A>G) and A59V (AF536174.1:g. 321C>T), as well as the microsatellite BM1500 (3.9 kb downstream), were genotyped. The measures of body weight and ultrasound examinations (rib eye area, back, and rump fat thickness) were performed in 3 different periods of animal management. During the first period, the animals were fed with grass and mineralized salt ad libitum. In the second period, they received grass and concentrate, and in the third, only concentrate. After the slaughter of animals, data were collected for classification and typification of carcasses. No significant association was found between the variables assessed and SNP -1457. Conversely, SNP A59V was associated with rump fat thickness and muscle color post-slaughter. BM1500 was associated with rump fat thickness in the first period (pre-slaughter), subcutaneous fat thickness 3003 ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 13 (2): 3002-3012 (2014) Leptin gene variations in Nellore cattle in the second, weight of the animals in the third, and length of the carcass after slaughter. These results suggest that SNP A59V and the microsatellite BM1500 might be useful for marker-assisted selection in Nellore cattle.

Advances in DNA technology have created biotechnological tools that can be used in animal selection and new strategies for increasing herd productivity and quality. The objective of the present work was to associate the genotypes of leptin gene exon 2 polymorphisms with productive traits in Nellore cattle. Blood was collected from Nellore males and PCR-RFLP reactions were performed with the restriction enzymes Cla I and Kpn 2I. The gene frequencies resulting from digestion by Cla I were 0.60 and 0.40 for allele A and T, respectively; the genotypic frequencies were AA = 0.20 and AT = 0.80. The gene frequencies from digestion by Kpn 2I were 0.81 for allele C and 0.194 for allele T; the genotypic frequencies were CC = 0.62 and CT = 0.38. The populations in both cases were not in Hardy-Weinberg equilibrium (p > 0.05), and the TT genotype was not found. Significant associations were noted between leptin gene exon 2 polymorphisms and five productive traits in Nellore cattle: carcass fat distribution, the intensity of red muscle coloration, pH, marbling, and post-slaughter fat thickness.

Recent molecular tools and technologies have marked the discovery of the origin and domestication processes of a wide variety of species, using either genomic or mitochondrial molecular markers to provide input for selection programs, as well as the management and conservation of animal breeds. This study aimed to analyze genes of mitochondrial DNA of the following sheep (Ovis aries) breeds: Pantaneira, Bergamácia, Dorper, White Dorper, Ile de France and Hampshire Down, to obtain their population genetic parameters and investigate the origin of these sheep populations reared in the State of Mato Grosso do Sul. The analysis of mitochondrial DNA allowed to infer an their phylogenetic relationships and revealed significant differences among them when compared with each other and with sequences obtained from GenBank. Through the formation of haplotypes, it was noted that the Pantaneira breed served as the maternal basis for the formation of the other breeds reared in the region, and it was possible to suggest a European origin for the sheep populations studied.

O sequenciamento de Sanger, ou identificação das bases moleculares do DNA por terminação da cadeia, é um dos métodos amplamente utilizados para estudos moleculares. O uso da região citocromo b do DNA mitocondrial como marcador molecular se justifica pela presença de regiões conservadas e variáveis que podem ser sequenciadas e utilizadas em análises filogenéticas em diferentes níveis taxonômicos. O objetivo deste trabalho foi avaliar a variação do DNA mitocondrial por meio de sequenciamento de Sanger. Para tanto, amostras de tecido sanguíneo de ovinos do grupamento genético Pantaneiro (n=14), Bergamácia (n=4), Dorper (n=5) e Ile de France (n=5) foram utilizadas para extração de DNA. Logo em seguida as amostras foram submetidas a procedimentos de amplificação, purificação e sequenciamento. As análises estatísticas foram realizadas nos programas BioEdit 7.3.1.0 e MEGA 5.10. A utilização de primers internos e externos possibilitou o sequenciamento de 86% da região do citocromo b, o que indicou menor perda de nucleotídeos que acontece na reação de sequenciamento com apenas um par de primers. Os cálculos de diversidade média da região sequenciada permitiram observar baixa variação genética na população, evidenciando a natureza conservada do DNA herdado maternalmente. O sequenciamento parcial da região do citocromo b foi capaz de mostrar a variação do DNA mitocondrial em ovinos de 4 raças diferentes e proporcionou gerar dados para a realização de estudos futuros de origem e evolução dos animais.

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