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.
A woman cannot ovulate more than once during each cycle. Therefore, she cannot get pregnant more than once during a cycle. Multiple ovulation can occur and is when two or more eggs are released in a single cycle. Both eggs are released during one 24 hour period and are responsible for the birth of fraternal twins.