Genotypes of Iranian Zel sheep for Calpastatin (CAST) locus were determined by polymerase chain reac-tion-restriction fragment length polymorphism (PCR-RFLP) and polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) methods and for Calpain (CAPN) locus by PCR-SSCP. Blood samples were collected from 200 purebred Zel sheep of Zel Breeding Station located in Golestan province in northeast of Iran. Extraction of genomic DNA was based on modified salting out method. The digestion of PCR products of CAST gene by MspI and NcoI restriction enzymes revealed two alleles M and N, with frequencies 85.5 and 14.5%, respectively. Frequencies were 75, 21 and 4% for MM, MN and NN genotypes, respectively. Alternatively, using PCR-SSCP method, four genotypes including AA, AB, BB and AC with frequencies of 71, 21, 4 and 4%, respectively, were observed in this population. Analyzing CAPN gene by the PCR-SSCP method, revealed two different conformational patterns (AA and AB) with frequencies of 69 and 31% for AA and AB, respectively. Average heterozygosity for both loci was low (0.28 and 0.25% for CAST using PCR-SSCP and PCR-RFLP, and 0.26% for CAPN). Yearling weights (YW) were analyzed by a statistical model comprising PCR-SSCP and as a result CAPN genotypes had significant effect (P<0.01) on YW. A Chi-square test confirmed Hardy-Weinberg (H-W) equilibrium for the CAST locus using PCR-SSCP method but not for PRC-RFLP method and CAPN locus. Totally, the investigated herd had little ge-netic diversity and different factors disturb H-W equilibrium and PCR-RFLP and PCR-SSCP might be used successfully in these studies.

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