ABSTRACT
Polymorphisms in 5'-flanking region of prolactin [PRL], exon 2 and exon 5 of prolactin receptor [PRLR] genes and its association with growth and egg traits were examined in breeder hens of Mazandaran native fowls breeding station. A single nucleotide polymorphism at site C-2402T and a 24 bp nucleotide sequence insertion at situation -382 in 5'-flanking regions of PRL gene were identified. PCR amplification together with Restriction Fragment Length Polymorphism [RFLP] and direct agarose gel electrophoresis were used to identify different genotypes at C-2402T and a 24 bp indel [insertion-deletion] at the site of -358 of PRL gene, respectively. Nucleotide substitution of C to T and a 24 nucleotides insertion [I] or deletion [D] in promoter region of PRL gene resulted in three genotypes with the frequency of CC [0.10], CT [0.84], TT [0.06] and II [0.39], ID [0.40], DD [0.21], respectively. There were no heterozygous females and only two genotypes A/A [0.54], B/B [0.46] and AA [0.72], BB [0.28] were identified in exon 2 and exon 5 of PRLR gene using PCR-Single Strand Conformation Polymorphism [PCR-SSCP] and PCR-RFLP analyses, respectively. A novel mutation consists of a BamHI restriction site found in the exon 5 of PRLR gene. The results showed significant association between SNP in exon 2 with body weight at hatch, age at sexual maturity, and between SNP in exon 5 and egg number. Individuals with AA genotype produced higher eggs than BB genotype [P<0.05]. These results showed that the PRLR locus can be considered as a major gene that may influence the production traits in chicken