The objective of this work was to sequence the MyoD1, MyoG, MyF5, MyF6, and MSTN genes and to identify polymorphisms in Santa Inês sheep (Ovis aries). A total of 192 lambs with 240 days of age were evaluated, and these genes were sequenced to be compared with the reference sequence in the Ovis aries genome. Genotype and allele frequencies were estimated, and the Hardy-Weinberg equilibrium was tested. Fragments containing 2,493 bp (MyoD1), 1,836 bp (MyoG), 2,813 bp (MyF5), 1,126 bp (MyF6), and 2,380 bp (MSTN) were obtained, and, in these sequences, 160 variants were identified. These polymorphisms were distributed as follows: 59 (MyoD1), 24 (MyoG), 63 (MyF5), 4 (MyF6), and 10 (MSTN). One hundred and four were novel polymorphisms, 45 in MyoD1, 2 in MyoG, 56 in MyF5, and 1 in MSTN. Regarding site, 61 were in intron (27 in MyoD1, 16 in MyoG, 5 in MyF5, 3 in MyF6, and 10 in MSTN), 87 in coding region (22 in MyoD1, 8 in MyoG, 56 in MyF5, and 1 in MyF6), and 12 on 3’UTR (10 in MyoD1 and 2 in MyF5). Therefore, the MyoD family and MSTN genes have several polymorphisms in Santa Inês sheep, which can be useful for association studies.O objetivo deste trabalho foi sequenciar os genes MyoD1, MyoG, MyF5, MyF6 e MSTN e identificar polimorfismos em ovinos Santa Inês (Ovis aries). No total, 192 cordeiros com 240 dias de idade foram avaliados, e estes genes foram sequenciados para comparação com a sequência-referência no genoma de Ovis aries. As frequências genotípicas e alélicas foram estimadas, e o equilíbrio de Hardy-Weinberg, testado. Foram obtidos fragmentos contendo 2.493 pb (MyoDl), 1.836 pb (MyoG), 2.813 pb (MyF5), 1.126 pb (MyF6) e 2.380 pb (MSTN), e, nessas sequências, foram identificadas 160 variantes. Esses polimorfismos foram distribuídos da seguinte forma: 59 (MyoD1), 24 (MyoG), 63 (MyF5), 4 (MyF6) e 10 (MSTN). Foram encontrados 104 novos polimorfismos, sendo 45 no MyoD1, 2 no MyoG, 56 no MyF5 e 1 no MSTN. Com relação ao local, 61 variantes estavam em íntron (27 no MyoD1, 16 no MyoG, 5 no MyF5, 3 no MyF6 e 10 no MSTN), 87 em região codificante (22 no MyoD1, 8 no MyoG, 56 no MyF5 e 1 no MyF6) e 12 na região 3’UTR (10 no MyoD1 e 2 no MyF5). Portanto, os genes da família MyoD e o MSTN possuem vários polimorfismos em ovinos da raça Santa Inês, os quais podem ser úteis em estudos de associação
