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.
Identical twins may or may not share the same placenta. Identical twins develop when a fertilized egg splits. Depending on when the split occurs will determine if the twins s â¦ hare a placenta, with either one or two chorions and amnions, or if they each develop their own placentas. 3 people found this useful.