In what biological process does imprinting primarily occur?

Imprinting primarily occurs during gene expression. This process involves the epigenetic modification of genes such that they are expressed in a parent-of-origin specific manner. This means that certain genes are activated or silenced depending on whether they have been inherited from the mother or the father. The implications of genomic imprinting are most evident in certain developmental processes, where the expression of these imprinted genes is crucial for normal growth and development.

In contrast, fertilization refers to the union of sperm and egg, while cell division involves processes such as mitosis and meiosis, where genetic material is replicated and divided. Protein synthesis is the process by which cells build proteins based on the genetic instructions encoded in DNA. Although these processes involve gene expression indirectly, they do not encompass the specific mechanisms of imprinting itself, where the focus lies on the regulation and expression of imprinted alleles rather than the broader processes of cell division or protein synthesis.