Question

Modifications to chromatin can affect transcriptional activity by changing the accessibility of DNA. When DNA is tightly wound, the DNA cannot be accessed by the transcription machinery. The following descriptions of various processes may or may not cause remodeling of chromatin. Match each description to the effect it has on transcriptional activity, but only if that effect is caused by chromatin remodeling.
Descriptions:
a. Activates
b. Inactivates
c. Activates and inactivates
d. No effect


1. Histone methylation occurs at different amino acids.
2. A transcriptional activator binds an enhancer sequence.
3. Histone acetyltransferases attach acetyl groups to the N-terminus of histones.
4. Histone deacetylases remove acetyl groups from the N-terminus of histones.

Answer 1

Answer:

1. Histone methylation occurs at different amino acids- activate or inactivate

2.  A transcriptional activator binds an enhancer sequence- activate

3.  Histone acetyltransferases attach acetyl groups to the N-terminus of histones- actiavte

4. Histone deacetylases remove acetyl groups from the N-terminus of histones- inactivate

Explanation:

1. Histone methylation is a process by which methyl groups are added to the histone proteins and may affect the transcription. The methylation of histone may activate or inactivate transcription depending on the amino acid is methylated.

2. Transcription activators are the proteins which bind to the enhancer sequence of DNA. This binding activates the transcription.

3. Histone acetylation adds an acetyl group to the histone amino acid at N- terminal which neutralizes the positive charge of the amino acid and the DNA is free.

4. Histone deacetylation is the process which removes the acetyl group from the histone amino acid and thus decreases the transcription rate.