How do epigenetic modifications affect gene expression?

Epigenetic modifications play a crucial role in regulating gene expression without altering the underlying DNA sequence. These modifications, which can include the addition of chemical groups such as methyl groups or the modification of histones, affect the accessibility of the DNA to transcription machinery. This means that they can enhance or suppress the transcription of specific genes, thereby determining whether genes are expressed (turned on) or silenced (turned off).

By influencing how genes are activated or deactivated, epigenetic modifications are essential in processes such as development, cell differentiation, and response to environmental factors. This regulatory capability allows for a dynamic adjustment in gene expression that can be altered in response to various stimuli, making it a fundamental concept in understanding genetics and disease.

The other options do not accurately represent the nature of epigenetic modifications: they do not change the DNA sequence itself, they do not permanently inactivate genes—many modifications are reversible—and they indeed have significant effects on protein production as they regulate gene expression.