应用微卫星DNA基因分型技术进行双生子卵型鉴定

目的 用微卫星DNA基因扫描和分型技术建立双生子卵型鉴定法。方法 选取69对同性别双生子、6对异性别双生子和17对同胞对，抽提基因组DNA，单盲设计，随机编号后，采用9对荧光标记的，在中国人群中具有高度杂合度的短串联重复序列（short tandem repeat,STR)引物，进行基因扫描和分型分析。根据这9个STR基因型的一致性来鉴别卵型。结果 9个STR基因型完全一致的63对受检者全部为同性别双生子，6对异性别双生子和17对同胞对的STR基因型均不完全一致，另有6对同性别双生子的STR基因型也不完全一致，经计算采用6个或5个STR位点判定同性别同卵双生的可信性分别大于99.6%和99%，采用全部9个位点判定同性别同卵双生的可信性大于99.95%。结论 STR基因扫描和分型技术为在基因组水平上直接判别双生子卵型，提供了一种准确，可靠的鉴定方法，它还有快速，简便等优点。

Use of microsatellites in zygosity diagnosis of twins

Objective To diagnose zygosity of twins by microsatellite polymorphism.Methods One hundred and eighty-four samples, including 69 pairs of twins with the same gender and 6 pairs of twins with different gender were recruited. Seventeen sib pairs were also collected for controls. Nine highly polymorphic microsatellite loci were amplified by polymerase chain reaction (PCR) using fluorescence-labeled primers and the products were sized by automated fragment analysis after electrophoresis and laser detection. Zygosity was diagnosed by comparing the concordance of the genotype of the 9 markers. Results Sixty-three pairs of monozygotic (MZ) and 12 pairs of dizygotic (DZ) twins were assigned their zygosity by comparison of polymorphism of 9 microsatellite loci. Within each of the 63 monozygotic (MZ) pairs there was complete concordance. However, within each of the 12 dizygotic pairs and other 17 sib pairs, discordant loci were found. With five or six markers, the probability that any twin pair was MZ if all markers were concordant was 99% or 99.6%, respectively. With all the nine markers, the probability that any twin pair was MZ if all markers were concordant was 99.95%. Conclusion The technology of gene scan and genotyping provides a rapid and reliable approach to zygosity detection.