BBC NEWS Programmes India's twins pose DNA puzzle:
By Rajan Chakravarty
BBC in Mohammad Pur Umri
Scientists from around the world are flocking to a small Indian village to try to find out why an extraordinarily large number of identical twins are being born there.
One in 10 births in Mohammad Pur Umri, near Allahabad, involves twins, most of them identical.
Looking at the faces of Umri's residents, you can be forgiven for wondering if you have stepped onto the set of a sci-fi film on cloning.
Globally, the odds of a woman giving birth to identical twins is one in 300.