Question

Thinking ahead to the remaining topics, what happens to histones bound to eukaryotic chromosomes before and during DNA replication and transcription?

Answer 1

Histones are the main proteins in chromatin.

Before DNA replication, histones bind with DNA very tightly. Chromosomes are composed of DNA tightly-wound around histones. Chromosomal DNA is packaged inside microscopic nuclei with the help of histones.

During DNA replication, what is kknown is that the histones detach and than they randomly end up on one of the two strands ( the old and the newly sythetized ), then new histones ( since the old ones were distributed within the old strand and the new strand, you ideally still need half of the histones to cover the whole old and new strand ) are synthesized and distributed along the two strands.

Before transcription, Methylation and demethylation of histones turns the genes in DNA "off" and "on,” respectively, either by loosening their tails, thereby allowing transcription factors and other proteins to access the DNA, or by encompassing their tails around the DNA, thereby restricting access to the DNA.

During transcription, histone survival is accompanied by the formation of a small transient DNA loop on the surface of the histone octamer including a molecule of transcribing enzyme. Efficient recovery of histones associated with DNA during passage of RNA Polymerase II (Pol II) is essential for cell viability.