Do identical twins have different fingerprints, irises, DNA and retinae?
Ok, people have given very different answers here, so I’ll try and clear it up a bit. Identical twins do have the same DNA for the most part, but it would not be identical on every base pare. But how the genetic matieral is expressed can differ vastly. Gene expression can depend on environment, so different twins can have a different expression rate of the same gene, depending on different environmental factors. Also, female identical twins can differ what X chromosome they have inactivated. In females, only one X chromosome is active, the other gets inactivated very early on in fetal development into what is called a barr body. This inactivation is largely random, and if the twins get different barr bodies inactivated they can have a very different X-linked gene expression. The fingerprints are different, they depend both on genes and development in the uterus, so identical twins will have similar patterns, since they have the same genes and a very similar environment, but not exactly
