Â· 4 years ago. A mutation is a change in the genetic material of an organism. We are made from trillions of cells, each with a nucleus composed of DNA â a set of instructions that tells the cell what to do. Cells copy themselves with astonishing accuracy, but every now and then a piece of code is copied incorrectly.
Identical (or monozygotic) twins happen when a fertilized egg splits into two separate babies-usually within the first twelve days of Mom's pregnancy. After twelve days, the egg may not split entirely and result in conjoined twins.
There are a couple of ways that multiples are conceived: * Multiple eggs are released or there is more than one ovulation. Both (or more) eggs are fertilized and you have fraternal twins. This can happen with or without fertility drugs. * One egg is release but splits in two. Identical twins are made. This can happen with or without fertility drugs.