Final answer:
Modifying the charge of histones affects DNA affinity for the octamer, chromatin compaction, and gene expression. Chemical modifications like acetyl groups relax the binding of DNA to histones, increasing affinity for the octamer. These modifications also alter chromatin structure, allowing some regions to be opened or closed for transcription. Opening the promoter region of a gene allows transcription to occur, while closed configuration prevents it.
Step-by-step explanation:
Modifying the charge of histones can affect three key aspects of gene regulation: DNA affinity for the octamer, chromatin compaction, and gene expression. Firstly, histone charge modifications can change how tightly the DNA molecule is wound around the histone proteins. When histones have a large positive charge, DNA is densely packed, resulting in low affinity for the octamer. But when the charge becomes less positive due to chemical modifications like acetyl groups, DNA binding to histones is relaxed and affinity for the octamer increases. Secondly, histone charge modifications influence chromatin compaction. By altering the location of nucleosomes and the tightness of histone binding, some regions of chromatin can be opened for transcription, while others can be closed. Finally, these modifications to histones also impact gene expression. Opening the promoter region of a gene allows RNA polymerase and transcription factors to bind and initiate transcription, leading to gene activation. Conversely, closed chromosomal configuration prevents access of these proteins to the DNA and transcription cannot occur.