Things I've learned this week

Do identical twins have the same DNA ?

Identical twins, formed when one fertilized egg splits, are the only people in the world with identical DNA. Fraternal twins, on the other hand, are formed when two different eggs are fertilized. Genetically speaking, fraternal twins are no closer than normal siblings, sharing only about 50% of their genes. Although identical twins have the same genotype, or DNA, they have different phenotypes, meaning that the same DNA is expressed in different ways.

Traits determined by phenotype, such as fingerprints and physical appearance, are the result of "the interaction of the individuals' genes and the developmental environment in the uterus." Thus, a DNA test can't determine the difference between identical twins, while a simple fingerprint can.

So now you know.