Genotypes for melatonin receptor type 1A (MTNR1A) and Calpastatin (CAST) were determined by enzymatic digestion of PCR products and Calpain (CAPN) genotype detected by PCR-SSCP method in Iranian Karakul sheep. Blood samples were collected from 100 purebred Karakul sheep. The extraction of genomic DNA was based on guanidinium thiocyanate- silica gel method. PCR amplicons were digested with restriction enzymes Mnll and MspI for MTNR1A and CAST genes, respectively. The MTNR1A locus had two alleles with frequencies of 0.79 for (+) and 0.21 for (-) alleles. Allelic frequencies for CAST locus were 0.85 for M and 0.15 for N. In addition, Calpain had two alleles A and B with respective frequencies of 0.79 and 0.21. The observed heterozygosity values for MTNR1A, Calpastatin and Calpain locus were 0.42, 0.29 and 0.35, respectively. The X2 test confirmed the existence of Hardy-Weinberg equilibrium for the three loci in the population. The data showed a large variation in studied genes. The genetic polymorphism could be regarded as useful tool for selection programs based on marker- assisted selection between different genotypes of those loci.

The ovine melatonin receptor 1A (MTNR1A) and aromatase (CYP19) genes were structurally characterized and the association between their variants and reproductive and growth traits was studied in Kurdi sheep at Kurdi sheep breeding station located in Shirvan, Iran. The genomic DNA was extracted by guanidine thio-cyanate-silica gel method. Polymerase chain reaction was carried out to amplify 824 bp fragment of exon 2 of MTNR1A and 140 bp fragment of the exon 3 of the ovine CYP19 genes. The PCR products were digested with restriction endonucleases RsaI for MTNR1A and BstMBI for CYP19 genes and checked by poly-acrylamide gel electrophoresis for the presence of restriction sites. Two alleles were found for all the loci investigated, which were named as A and B for CYP19, and R and r for MTRN1A. Allelic frequencies for MTRN1A were 0.49 and 0.51 for R and r alleles, while in the case of CYP19 gene, frequencies were 0.475 and 0.525for A and B alleles, respectively. Association analysis did not show any significant relations be-tween MTNR1A gene polymorphisms and litter size (LS), age at first lambing (AFL) and lambing interval (LI). Moreover, CYP19 gene polymorphism did not affect birth weight (BW), weaning weight (WW), 6, 9 and 12 months (YW) body weights, age at first lambing (AFL) and lambing interval (LI).

The objective of this study was to evaluate the relationship between polymorphism at the MnlI site of MTNR1A gene and production traits of Shal and Romanov crossbreeding. The crossbreeding between Shal and Romanov was done on 600 Shal ewes. For this reason, Shal ewes were laparoscopic ally and artificially inseminated with the semen of Romanov breed. For the preparation of genomic DNA, a total of 90 ewes, either Shal (n=50) or Shal × Romanov (n=40), were used and an 824 bp fragment of exon 2 of the MTNR1A gene was amplified. In this research, two genotypes MM and Mm were detected in the study Shal popula-tion with frequencies of 0.78 and 0.22, respectively, while MM and mm genotypes of the study crossbreeds were detected with 0.125 and 0.0875 frequencies, respectively. However, the mm and Mm genotypes were not detected in Shal and Shal ´ Romanov crossbreeds, respectively. The MnlI marker site in Shal ´ Ro-manov breeds had a significant effect (P>0.05) on body weight after 3 months (BW3) as the ewes with MM genotypes had significantly higher BW3 than mm individuals. However, no significant difference was ob-served between MM and mm marker sites for birth weight (BW) and 6-month body weight (BW6). The same results were observed for Shal breeds as when MM and Mm genotypes were detected for BW, BW3 and BW6 traits. In conclusion, in this study, mm genotype as a measurement for litter size in sheep breeds was successfully introduced into Shal ´ Romanov crossbreeds, while their production traits were not af-fected by MnlI genotypes.

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.

The influence of melatonin receptor 1A gene on litter size was studied in 150 ewes from Zel (n=100) and Naeini (n=50) sheep breeds. Two restriction fragment length polymorphism (RFLP) analyses were done to determine all genotypes occurring by variations at MnlI and RsaI restriction sites. The M and C were the most frequent alleles in both of these breeds. The MM genotype was predominant in Zel and Naeini breeds (0.52 and 0.60, respectively). The CT genotype (0.45) has the highest frequency in Zel and the CC genotype (0.44) was predominant in Naeini breed. The MMCT genotype was identified with the highest frequency of 0.25. There were no significant differences between melatonin receptor 1A (MTNR1A) genotypes and litter size in Naeini ewes. But it seems that selection of animals with mm and Mm genotypes can progress mean litter size in Zel breed. The positive effect of mC and mT alleles was significant on lambing rate in Zel and Naeini breeds. However, the mmCT genotype has considerably greater mean litter size than the other ones. Finally, the MTNR1A polymorphism can explain only a small part of the genetic variability on seasonal sexual activity between these breeds. Therefore, the implication of other genes must be noticed.