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.
This occurs when two sperm fertilize one egg which then later splits. These types of twins were acknowledged in 2007 in a pair of 3 year old multiples. Twins who have Different Fathers. When a woman releases more than one egg and has different sexual partners who both fertilize an egg each.