How can chromatin marks be inherited during cell division?

• A. Methylation patterns and histone modifications can be propagated to daughter cells, maintaining gene expression states
• B. They are erased every cell division
• C. They are encoded in DNA sequence changes
• D. They are transmitted only through germ cells

Answer: (A)

Chromatin marks can be inherited through cell division because epigenetic information is maintained during replication. DNA methylation patterns are copied to the new DNA strand by maintenance methyltransferases, so the methylation state that helped regulate gene activity in parent cells is preserved in daughter cells. For histone marks, parental histones carrying specific modifications are redistributed to the two daughter DNA molecules, and the local chromatin environment is re-established by histone chaperones and histone-modifying enzymes that write the same marks on neighboring nucleosomes. This combination of copying DNA methylation and propagating histone modifications allows cells to retain gene expression states across divisions, which underpins cellular identity and development.

Some marks can be reset in special contexts, such as germline reprogramming or early embryogenesis, but in most somatic divisions these chromatin states are retained to maintain memory of gene activity. This is why the idea that these marks are erased every division is not accurate, and why they are not simply encoded by DNA sequence changes. Also, while germline transmission can transfer some epigenetic information, chromatin marks are not restricted to germ cells—they are inherited mitotically in somatic cell lineages as well.