Abstract: In order to understand the codon characteristics of GnRHR gene and select the appropriate exogenous expression system, online tools CUSP, CHIPS and CodonW software were used to analyze the codon characteristics of GnRHR gene. GnRHR gene was compared to other genes of chicken, model animal genomes and GnRHR gene of other species.The results showed that ENc value of GnRHR gene in Jinghai Yellow chicken was small, which indicated strong codon bias. GnRHR gene was bias toward the synonymous codons with G and C at the third codon position. GC content was greater than AT content in CDS region of GnRHR gene. Analysis by CodonW software showed that in codons of GnRHR gene in Jinghai Yellow chicken, GCC, ATC, CTC, CTG, CGC, CGG, AGC, TCC and GTG were of strong bias and end with G/C. There were 12 bias codons with G/C at the third codon position in 31 genes of chicken. Codon bias comparison to other species showed that difference between GnRHR gene and the three species were very large, which indicated that GnRHR gene was not suitable for exogenous expression. GnRHR gene of poultry bias toward the synonymous codons contained G/C or end with G/C. GnRHR gene of our species had no strong codon bias. Result of clustering based on RSCU value showed that species with close genetic relationship tend to have similar codon bias.

Key words: Jinghai Yellow chicken; GnRHR gene; codon bias