Question: You isolate a mutant strain of mice that grow at an unusually fast rate, perform a blood test on …

You isolate a mutant strain of mice that grow at an unusually
fast rate, perform a blood test on the mice, and find that they
have elevated levels of insulin-like growth factor. The phenotype
is the result of a mutation in a region of the genome containing a
gene encoding a DNA methylase. What kind of mutation is causing the
rapid growth of these mice