DNA and Chromatin Regulation Flashcards
DNA is packed into chromosomes in the form of
Chromatin
Chromatin is a combination of
Histone proteins, DNA, and non-Histone proteins
Chromatin has repeating units which are called
Nucleosomes
What are Nucleosomes?
Repeating units of chromatin made of 146 base pairs of double helical DNA that is wrapped around 8 histones
What are 4 types of Histones?
- H2A
- H2B
- H3
- H4
Where does Acetylation occur?
At the amino terminal tails of histone proteins
Acetylation is done by the enzyme
Histone Acetyltransferase
What is the enzyme which reverses Acetylation?
Histone Deacetylase
What does Histone Deacetylase allow for?
The condensed chromatin structure and less transcription of those genes
What is Acetylation?
The uncoiling of chromatin structure, allowing for it to be accessed by the transcription machinery for expression of genes
What is Epigenetic Regulation?
Modifications that regulate gene expression are inheritable
What are two forms of DNA?
- Heterochromatin
- Euchromatin
What is Euchromatin?
Less densely packed DNA and transcriptionally active
What is Heterochromatin?
Densely packed DNA and transcriptionally inactive
What is combined with DNA Methylation?
Histone Deacetylation
Histone Deacetylation occurs during
Gene Silencing
What is Gene Silencing?
More permanent method of down-regulating the transcription of genes
What is DNA Methylation?
The addition of a methyl group to the cytosine via enzyme Methyltransferase
DNA Methylation occurs where?
In Cytosine-rich sequences, or CpG Islands
What does DNA Methylation alter?
The expression of genes
DNA Methylation occurs as
Cells divide and differentiate from embryonic stem cells to different tissues
DNA Methylation is associated with
Genomic imprinting and X-chromosome inactivation
How can DNA Methylation affect gene transcription?
- May physically impede the binding of transcriptional proteins to the gene
- Methylated protein may be bound by methyl CpG-binding domain proteins
What can methyl CpG-binding domain proteins recruit?
Additional proteins to the locus which modify histones and form heterochromatin
