Final answer:
The cell distinguishes between maternal and paternal chromosomes for the purpose of imprinting through epigenetic marks established in the parental germ cells. Imprinting results in the silencing of a gene based on its parent of origin. This intricately regulated process ensures that offspring express the appropriate gene alleles.
Step-by-step explanation:
How Cells Determine Maternal vs Paternal Chromosomes for Imprinting
During sexual reproduction, chromosomes are inherited from both parents. A maternal chromosome is derived from the mother’s egg, while a paternal chromosome comes from the father's sperm. When considering the chromosomal inheritance of offspring like the Igf2 gene on chromosome 7 (chr7), each cell has copies of both the maternal and paternal chromosomes. The concept of imprinting refers to an epigenetic phenomenon where certain genes are expressed in a parent-of-origin-specific manner. This means that the gene from the mother could be silenced if it is maternally imprinted, or the gene from the father could be silenced if it is paternally imprinted.
Epigenetic marks, such as DNA methylation patterns or histone modifications, are established in the parental germ cells and maintained through cell divisions. These marks serve as the cellular mechanism for distinguishing between maternal and paternal chromosomes, guiding which genes are to be imprinted. The process of establishing these epigenetic marks and the subsequent imprinting is a complex one involving the interplay of multiple regulatory regions and is guided by the developmental history of the gametes. Once the imprinting marks have been established in the germ cells, they instruct the offspring's cells on how to treat each copy of the gene, ensuring the appropriate expression pattern is followed.