Final answer:
Epigenetic modifications can have either inactivating or activating effects on gene expression. One example of an inactivating mark is DNA methylation, which silences genes. One example of an activating mark is acetylation of histone proteins, which increases gene expression.
Step-by-step explanation:
Epigenetic modifications can have either inactivating or activating effects on gene expression.
One example of an inactivating mark is DNA methylation. This is the addition of a methyl group to the DNA molecule, which can prevent the binding of transcription factors and other proteins necessary for gene expression. Methylation can result in the silencing of genes.
One example of an activating mark is acetylation of histone proteins. Histones act as spools that DNA wraps around, and acetylation of histones can loosen the packaging of DNA and make it more accessible to transcription factors. This can lead to increased gene expression.