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.
The difference between fraternal and identical twins is that fraternal twins are two separate eggs fertilized by two separate sperm to form two separate embryos and then make two separate babies.Identical twins are formed when one fertilized egg divides into two separate embryos to make two babies.raternal, or dizygotic, twins happen when Mom releases two eggs (either at the same or different times during her cycle), and different sperm fertilize each egg. Fraternal twins share up to 50% of their genes, and are no more alike or different than any two siblings would be.