一、(50%)

1. (10%) Identical twins (同卵雙胞胎) form when a single fertilized egg splits into two genetically identical parts. The identical twins share the same DNA set and are thus always of the same sex. Fraternal (異卵雙胞胎) twins develop when two separate eggs are fertilized and implant in the uterus. The genetic connection is the same as siblings (兄弟姐妹) born at separate times. If 64 percent of all twin pairs are of the same sex, what percentage of twin pairs are identical twins?