Question

In what types of cells would you expect de novo methylation to occur? In what cell types would it not occur?

Short answer

De novo methylation would be expected to occur in stem cells during early development stages, particularly in totipotent and pluripotent cells. It would not occur in fully differentiated cells.

Step-by-step solution

Identify where de novo methylation occurs

De novo methylation, is the process of adding a methyl group to the DNA molecule, specifically to the cytosine residues. This process is primary in early embryonic development, particularly in totipotent and pluripotent stem cells. During this phase, the organism's DNA undergoes significant methylation in order to define specific patterns of gene expression necessary for the development and differentiation of the cells.

Identify where de novo methylation does not occur

In general, de novo methylation does not occur in fully differentiated cells. These cells have already established their gene expression and function within the organism, and do not require further modification of their DNA via methylation. Their functionality and identity are already defined by the methylation pattern established during the embryonic development stage.