Final Unit: Gene Expression Flashcards
What is gene regulation?
The ability of cells to control their level of gene expression
Prokaryotes and eukaryotes can control level of gene expression at the levels of …
Transcription, Translation, Post-translation
What are three additional levels of control are unique to eukaryotes?
- Chromatin remodeling
- RNA processing
- Regulation of mRNA life span or stability
What helps DNA condense into such a small size?
Nucleosomes
What are nucleosomes and how are they produced?
Smallest structural component of chromatin
DNA wraps around histones
After the nucleosome is formed, what is next?
The nucleosomes get formed into a 30 nm fiber
What happens to the fiber of nucleosomes?
It is looped into place within the nuclear matrix
What is chromatin remodeling?
When DNA near the promoter is released from tight interactions with proteins
Is DNA unaccessible when the chromatin is condensed or decondensed?
Condensed
What is chromatin?
A complex of DNA and proteins
What is euchromatin?
Lightly stained, more open (decondensed) chromatin
What is heterochromatin?
Darkly stained, more closed (condensed) chromatin
Which type of chromatin contains the majority of eukaryotic genes?
Euchromatin
Which type of chromatin is associated with low gene transcription?
Heterochromatin
In preparation for transcription, nucleosomes are altered by what?
Multiprotein complexes
What are the two types of chromatin remodeling?
- Local histone mobilization
- Histone modifications
In local histone mobilization, what do chromatin remodeling complexes use to reshape chromatin?
ATP
What are the four mechanisms for local histone mobilization?
- Unwrapping
- Sliding
- Ejection
- Dimer exchange
What are the three mechanisms that histone modifications use?
- Acetylation
- De-acetylation
- Methylation
What is the histone code hypothesis?
Particular combinations of histone modifications set the state of chromatin condensation for a gene
Which enzyme facilitates acetylation of histones?
Histone acetyl transferases (HATs)
What does HAT add? To where?
Negatively charged acetyl groups to the positively charged lysine residues in histones
What is the effect of histone acetylation?
Neutralizing a histone’s positive charge
What two things does histone acetylation weaken?
- Weakens histone-DNA interactions
- Weakens nucleosome-nucleosome interactions
What is the end result of acetylation?
Decondensed chromatin –> allow gene expression
Which enzyme facilitates de-acetylation of histones?
Histone deacetylases (HDACs)
What does HDAC remove? What is the effect of this?
Removes the acetyl groups from histones which therefore reverses the effects of acetylation