Question

When a cell synthesizes a protein, does it matter whether the mRNA comes from a maternal or a paternal allele of the gene that codes for the protein?

Answer 1

When a cell synthesizes a protein, it matters whether the mRNA comes from a maternal or a paternal allele of the gene that codes for the protein.
This is because female mammals have an additional system for differential allele expression - ChrX inactivation. In a tissue, one ChrX is randomly inactivated by heterochromatisation. Therefore, most of the gene on one ChrX are off. That is why, some cells in a tissue will express the maternal allele, while others the parental allele.