Melnick M, Myrianthopoulos N C, Christian J C
Am J Hum Genet. 1978 Jul;30(4):425-33.
The 7-year IQ scores (WISC) of 116 white and 143 black nonmalformed twins of known zygosity and placental type were ascertained from the NINCDS Collaborative Perinatal Project (NCPP). The type of chorion and zygosity had no significant effect on the mean IQ or among-pair variation. In white monozygotic twins, however, analysis of variance revealed a significantly greater within-pair mean square for dichorionic twins than monochorionic twins. On the other hand, the white dichorionic monozygotic (MZ) and dizygotic (DZ) within-pair mean squares were quite similar. These findings were not evident in blacks for either of the within-pair comparisons. In addition, estimates of genetic variance were dependent upon MZ chorion type in both races. These data suggest to us that (1) in white twin pairs dichorionic placentas are of greater influence than the similarity or dissimilarity of genomes with regard to intrapair IQ development, and (2) failure to consider chorion type may introduce a serious bias in the interpretation of genetic variance estimates of IQ variability.
从国立神经疾病与中风研究所协作围产期项目（NCPP）中确定了116名白人以及143名黑人非畸形双胞胎（已知合子性和胎盘类型）的7岁智商分数（韦氏儿童智力量表）。绒毛膜类型和合子性对平均智商或双胞胎对间差异均无显著影响。然而，在白人同卵双胞胎中，方差分析显示，双绒毛膜双胞胎的双胞胎对内均方显著大于单绒毛膜双胞胎。另一方面，白人双绒毛膜同卵（MZ）和异卵（DZ）双胞胎对内均方相当相似。在黑人的任何一对内比较中，这些发现均不明显。此外，两个种族的遗传方差估计均取决于MZ绒毛膜类型。这些数据向我们表明：（1）在白人双胞胎对中，就双胞胎对内智商发育而言，双绒毛膜胎盘比基因组的相似性或不相似性影响更大；（2）在解释智商变异性的遗传方差估计时，未考虑绒毛膜类型可能会引入严重偏差。
