THE failure to properly reactivate and then deactivate one of the two X chromosomes could be why many cloned cows die soon after birth.
A team at the University of Connecticut in Storrs compared five cloned female calves that died shortly after birth with normal cows and healthy clones. They found the dead clones had genes on one X chromosome switched on that should be switched off and vice versa.
What’s more, in the placentas of the animals that died, both X chromosomes appeared active. This could be why the placentas of some cloned embryos are abnormally large, the team suggests.…
