The big day provides the perfect excuse to don a little green, prepare a St. Patrick’s Day menu, take in a parade or two, sip ...

Identical twins (also called monozygotic or MZ twins) are conceived when a single sperm fertilizes a single egg and the resulting zygote divides in two. Because the zygote originated from the same ...

Identical twins arise from a single fertilized egg, or zygote, splitting into embryos with duplicate DNA, but what causes the split remains unknown. Zygote splitting was once thought ...

Those kids could be identical twins—kids of the same sex developed from a single zygote that splits and forms two embryos. They could also be fraternal twins, which are developed from a separate ...

Within hours of fertilisation, this new cell, called a zygote, divided into two identical ... the embryos create near-replicas of themselves. Identical twins. This quirk of nature has given ...