Epigenetics refers to heritable changes in gene expression not caused by changes in the DNA sequence. Which of the following is an example of an epigenetic modification?

• A. The process of DNA replication
• B. A mechanism by which RNA polymerase initiates transcription
• C. Heritable changes in gene expression not caused by changes in DNA sequence; e.g., DNA methylation or histone modification
• D. Changes in DNA sequence that alter gene expression

Answer: (C)

Epigenetics involves chemical changes to DNA or its packaging that regulate gene activity without altering the DNA sequence itself. An example is DNA methylation or histone modification, which can change how tightly DNA is wound and how accessible a gene is for transcription, and these marks can be inherited during cell division. The option that describes heritable changes in gene expression not caused by changes in DNA sequence directly captures this idea, including mechanisms like DNA methylation or histone modification. Other options describe processes that either copy the genetic material (DNA replication), regulate transcription without invoking a heritable chromatin change, or involve alterations to the DNA sequence itself—none of which are epigenetic modifications.