Objective:To study the differences of growth hormone recepto(rGHR)gene between normal mandible(control group)and protruding mandible(study group)in molecular level by comparing the gene’s nucleotide sequences.Methods:In our study

we selected 100 individuals with protruding mandibles and 87 individuals with normal mandibles by the study criterions

diagnosed in Affiliated Stomatological Hospital of Chongqing Medical University during 2005～2006.5 ml venous blood was withdraw and the genomic DNA was isolated from the whole blood cells with the use of a DNA Blood Kit.PCR amplification was performed by a standard protocol to increase and sequence the aim gene in normal and protruding individuals.And then we compared the acquired gene sequences with the published ones in NCBI(national center for biotechnology information)database

finally found the positions of single nucleotide polymorphism(SNP)in exon 10 of GHR gene and calculated the allele frequency and genotype frequency in study and control groups by SPSS10.0.Results:One SNP position(including study and control groups)was found in our study and his nucleotide code was 1673.In this SNP position

there were two alleles(AC)and three genotypes(AC

AA and CC).The allele frequency and distributions of genotype had a significant difference by χ2 calculation in 0.01 level.Conclusion:Differences in sequences of growth hormone receptor gene exist in individuals with protruding mandibles and individuals with normal mandibles.