Abstract: Abstract Objective: To investigate the genetic polymorphisms of 3 short tandem repeat (STR) loci D18S53, D18S58 and D18S488 on chromosome 18 in fetus of Tianjin Han population. The aim of the study was to discuss the evaluation criterion of quantitative fluorescence polymerase chain reaction (QF-PCR) and to provide basic data for the use of 3 STR loci in gene diagnosis and prenatal gene diagnosis of Edward syndrome (ES). Methods: Samples of villus and 374 amniotic fluid from gravida of Tianjin Han population were collected. QF-PCR and ABI PRISM 377 sequence were used. The frequencies of the genotypes were tested with Hardy-Weinberg equilibrium. Genetic analysis was performed to conclude some data of population genetics such as the frequency of the alleles, the heterozygosity of observation(Ho), the polymorphism information content(PIC), the probability of discrimination power(DP), and the probability of exclusion(PE). Results: 15, 13 and 15 alleles of D18S53, D18S58 and D18S488 were observed respectively. The frequencies of the genotypes were in good agreement with Hardy-Weinberg equilibrium. The Ho of 3 STR loci were 0.797, 0.847 and 0.792. The PIC were 0.81, 0.75 and 0.73. The DP were 0.944, 0.901 and 0.881. The PE were 0.593, 0.689 and 0.585. Conclusion: It was the favorable genetic markers of chromosome 18 that D18S53, D18S58 and D18S488 STR loci were, so they can be used in prenatal gene diagnosis of ES.

Key words: tandem repeat sequences, Edward syndrome, polymorphism, genetic, fetus, TIANJIN