Question

Explain how the compaction of DNA is achieved, what it typically signifies in terms of gene activity, and the molecular modifications that are associated with this transcriptionally silent state, particularly focusing on CpG islands and histone tails.

Answer 1

The compaction of DNA is achieved through chromatin remodeling and involves the wrapping of DNA around histone proteins. Compacted DNA typically signifies gene activity. Molecular modifications, such as DNA methylation and chemical modifications of histone tails, are associated with transcriptionally silent states.

Step-by-step explanation:

The compaction of DNA is achieved through a process called chromatin remodeling. In the first level of compaction, DNA wraps around histone proteins to form nucleosomes. This leads to the formation of chromatin fibers, which further condense the DNA. The compaction of DNA typically signifies transcriptional activity, with accessible DNA being associated with gene activity.

During compaction, there are molecular modifications that occur. One such modification is DNA methylation, which involves the addition of a methyl group to cytosine residues in CpG islands. This methylation is often associated with transcriptionally silent states. Additionally, histone tails can undergo chemical modifications, such as acetylation or deacetylation, which alter chromatin structure and influence gene expression.