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.
When the bodies of twins connect, they are called conjoined twins. Conjoined twins begin as a single fertilized egg. Usually, a single egg develops into 1 baby. Sometimes a single egg divides in half 1 to 2 weeks after itâs fertilized. This creates a set of identical twins.