DNA Packaging and Gene Regulation

These flashcards cover key concepts related to DNA packaging, histones, transcription regulation, and the effects of methylation and acetylation on gene expression.

Nucleosome

A structural unit of DNA that consists of a segment of DNA wrapped around a core of histone proteins.

Histones

Proteins that package and order DNA into structural units called nucleosomes.

Euchromatin

A form of chromatin that is less tightly packed, allowing access for transcription, often associated with acetylation.

Heterochromatin

A form of chromatin that is tightly packed, making it inaccessible for transcription, often associated with methylation.

Arginine

A positively charged amino acid abundant in histones that helps bind negatively charged DNA.

Lysine

A positively charged amino acid in histones that is subject to methylation and acetylation, affecting gene expression.

Transcription

The process of copying a segment of DNA into RNA.

Methylation

The addition of a methyl group to DNA or histones, often repressing transcription.

Acetylation

The addition of an acetyl group to histones, generally promoting gene transcription by loosening DNA binding.

CpG islands

Regions of the genome rich in cytosine and guanine nucleotides that can be methylated, affecting gene expression.

Histone H1

A histone protein that links nucleosomes together, but is not part of the nucleosome core.

Genomic repression

Regulation of gene expression leading to reduced transcription, often through methylation.

Transcriptional machinery

The collection of proteins and enzymes, including RNA polymerase, required for transcription.

Covalent modifications

Chemical alterations like methylation or acetylation that change histone affinity for DNA and affect transcription.

DNA affinity

The strength of the binding interaction between DNA and histones, influencing transcription accessibility.

Methyl groups

Chemical groups added to histones or DNA that can inhibit transcription when added to lysines.

Acetyl groups

Chemical groups added to histones that can increase transcriptional activity by loosening DNA from histones.

Gene transcription regulation

The mechanisms that influence the amount and timing of gene expression, including histone modifications.

Promoter methylation

The methylation of CpG islands in a gene's promoter region, leading to transcriptional repression.

Methylated histones

Histones that have had methyl groups added, generally associated with gene repression.

Active transcription

The process by which RNA polymerase transcribes a gene into RNA, often linked to euchromatin.