RESUMO
The genotypes of the melatonin receptor 1A [MTNR1A] were determined by PCR-RFLP in the native Iranian Shall and karakul breeds of sheep. Blood samples were collected from 60 karakul and 50 Shall breeds. Genomic DNA was extracted based on the Guanidin Thiocyanate-slica gel method. After PCR reaction, PCR products were digested by the Mnl1 restriction enzyme. The MTNR1A locus had two genotypes with frequencies of 0.7 [+ +] and 0.3 [+ -] in the Karakul breed, 0.58 [+ +] and 0.42 [+ -] in the shall breed. Heterozygosis value for the MTNR1A locus in Shall and Karakul breeds were 0.42 and 0.3, respectively. This study provided evidence that sheep breeds, Shall and Karakul have variability in MTNR1A locus. Therefore, this locus can be used as a marker for the reproduction trait in selection programs