Identical twins start life with the same genes from the same fertilised egg . As they age , the number of hydrogen bonds in the DNA changes due to different life experiences such as smoking and different diets . This is why identical twins have a slightly higher chance of having cancer than fraternal twins or even triplets ( which are more common ).
Identical twins start life with the same genes from the same fertilised egg . As they age , the number of hydrogen bonds in the DNA changes due to different life experiences such as smoking and different diets . By heating DNA until bonds break , researchers can spot these differences . This will help identify which twin is guilty in a criminal case , for example .