ned help with a question a level biologyWatch
Which of the following statements is/are correct?
Methylation of DNA prevents gene transcription.
The phosphate group of a DNA nucleotide becomes methylated
Acetylation of histone proteins causes DNA to become less accessible to transcription factors.
If so, what are your initial thoughts?
The addition of methyl groups (methylation) makes the histone proteins coiled around DNA more hydrophobic. As a result they bind more tightly to each other, causing DNA to coil more tightly and therefore preventing transcription of genes.
Therefore this statement is correct.
2: the methyl group is attached to a cytosine base, not to a phosphate group, so this is incorrect.
3: acetylation of histone proteins reduces the positive charge on the histones, making them more negative. This causes DNA (which is negatively charged) to coil less tightly, which allows more genes to be transcribed. The DNA becomes more accessible to transcription factors, so this statement is incorrect.