الفهرس 
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Abstract
This study was carried out for detection of polymorphisms in melatonin receptor 1A (MTNR1A) and Arylalkylamine N acetyltransferase (AA-NAT) genes and their association with reproductive traits. Blood samples of 126 Animal from three Egyptian sheep breeds were collected. DNA was extracted and subjected to PCR-RFLP using RsaI and SmaI enzymes. Two alleles (C and T), three genotypes (CC, CT and TT) for MTNR1A gene also (A and G), (GG, GA, and AA) for AA-NAT gene were detected. Alleles C and A, genotypes CT and GA showed the highest frequency for MTNR1A and AA-NAT genes respectively. Association analysis of MTNR1A SNP revealed a significant association in Ossimi and Rhmani breeds with age of first lambing and C allele seems to be the favorable allele. Results for AA-NAT SNP demonstrate significant differences in Ossimi with age of first lambing and litter size and in Rhmani with lambing interval and Quite discrepancy were observed for the favorable allele. Concerning to first conception season the study revealed that ewes carrying CT genotype of MTNR1A gene and conceive in UF season exhibited significantly the lowest age of first lambing and TT ewes conceived in LF have the highest litter size. Also, ewes carrying GG genotype of AA-NAT gene and conceive in EF or UF seasons exhibited significantly the lowest age of first lambing. Regarding lambing season TT ewes of MTNR1A SNP with lambing period in LF season and GG ewes of AA-NAT SNP with lambing period in UF season have significantly the lowest lambing interval. According to personal knowledge this is the first study concerned with this association in Egyptian sheep breed. In conclusion: the polymorphisms achieved in this study could be measured as genetic markers suitable for improving reproductive efficiency during unfavorable season and the obtained desirable genotypes could be taken into account in new genetic selective schemes.