1.What is the spreading phase of X-chromosome inactivation? Why do you think it is called a spreading phase? 2. When does the erasure and reestablishment phase of genomic imprinting occur? Explain why...

1.What is the spreading phase of X-chromosome inactivation? Why do you think it is called a spreading phase? 2. When does the erasure and reestablishment phase of genomic imprinting occur? Explain why it is necessary to erase an imprint and then reestablish it in order to always maintain imprinting from the same sex of parent. 3. In what types of cells would you expect de novo methylation to occur? In what cell types would it not occur?