This is huge step forward in human therapeutic cloning. However it's still incredibly inefficient and could lead to the stem cells having a higher probability o

This is huge step forward in human therapeutic cloning. However it's still incredibly inefficient and could lead to the stem cells having a higher probability of becoming cancerous. Nuclear transfer doesn't usually work in mammals because the DNA from the male and female differ, unlike in other animals. For the clone to be successful, the DNA needs to be rapidly "reprogrammed" by the egg (ie the methylation patterns changed) which could lead to genes being misexpressed and causing uncontrolled proliferation.