Rare success
The researchers spent time ensuring that the enzymes they had were modifying the methylation as expected, and that development started as usual. Their general finding is that the enzymes did change the methylation state for about 500 bases on either side of the targeted site, and did so pretty consistently. But there are seven different imprinting sites that need to be modified, each of which controls multiple nearby genes. So, while the modifications were consistent, they weren’t always thorough enough to result in the expected changes to all of the nearby genes.
This limited efficiency showed up in the rate of survival. Starting with over 250 reprogrammed
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