DAT Bootcamp Molecular Genetics Practice Test

Histone methylation can change how tightly DNA is packaged, influencing whether genes are accessible for transcription. When repressive methylation marks are present on histone tails in promoter or regulatory regions, they recruit proteins that promote a closed, condensed chromatin state (heterochromatin). This makes it harder for RNA polymerase II and transcription factors to access the DNA, leading to reduced transcription of the associated genes.

Translation relies on mRNA that’s already produced, so it isn’t directly controlled by histone marks. DNA replication and mutation rate aren’t the primary processes directly decreased by these histone modifications in the usual sense; chromatin state can influence replication timing and repair, but the clearest, most direct impact of repressive histone methylation is a decrease in transcription.