Final answer:
MZ twins may show differences in DNA methylation and histone acetylation patterns over time due to environmental factors, leading to changes in chromatin structure and gene expression. These epigenetic modifications influence not only the individual's gene regulation but also have potential trans-generational effects.
Step-by-step explanation:
Monozygotic (MZ) twins, although genetically identical at birth, may experience divergent changes in epigenetic patterns such as DNA methylation and histone acetylation as they age. Epigenetic modifications like these play a crucial role in chromatin remodeling, which influences gene expression by altering the structure from a compact 30nm fiber to a more accessible 'beads-on-a-string' nucleosome arrangement, and vice versa. Factors that can induce these alterations include environmental influences such as UV exposure, diet, toxins, and other life-style choices, impacting not just the individuals but potentially their offspring as well through trans-generational epigenetic inheritance.
In the context of female X chromosome inactivation during embryonic development, such epigenetic changes lead to tighter nucleosome packing and consequently reduced gene expression on the inactivated chromosome. When considering new therapeutic drugs, those that decrease DNA methylation or prevent the removal of acetyl groups from histone proteins can reactivate silenced genes, offering a strategy to target and kill tumor cells. Ultimately, these patterns of methylation and acetylation as we age reveal the dynamic nature of our genome and the profound effect of environment on gene regulation.