DNA Regulation Flashcards
What is a key regulatory process for DNA?
Acetylation of histones (euchromatin, active transcription) and deacetylation of histones (heterochromatin, inactive transcription) is a key regulatory process.
What is gene transcription controlled by?
A regulatory region near the site of transcription initiation.
Whether the regulatory regions are simple or complex, they contain features, short stretches of DNA of defined sequences (______) and gene regulatory proteins (_____) that recognize and bind these stretches of DNA
Cis-acting; trans-acting
What are some common DNA binding structural motifs?
- Helix-turn-helix
- homeodomain proteins: key regulator of animal development
- Zinc finger: has alpha helices and beta sheets coordinated by zinc atoms
- Leucine zipper: 2 alpha helices
- Helix-loop-helix
Summarize when the Lac Operon is on or off.
When glucose is present, cAMP decreases, thus CAP is not bound.
When glucose is absent, cAMP is present, CAP is bound.
When lactose is absent, Lac repressor is bound.
When lactose is present, Lac repressor is absent.
Only condition where Lac operon works is when glucose is absent (CAP is bound) and lactose is present (Lac repressor is absent).
What does a eukaryotic gene regulatory region consist of?
A promoter plus regulatory regions that may be tens of thousands of base pairs away.
Define enhancers.
Regulatory sites that are distant from the promoter.
Many gene regulatory proteins consist of at least two domains, what are these two domains?
- A structural motif that recognizes specific DNA sequences
- An activation domain that accelerates transcription
Define insulators.
DNA sequences that prevent regulatory proteins from influencing distant genes .
Define epigenetics.
Heritable (meiosis, mitosis), reversible changes in the genome (no change in sequence) that regulate gene expression, most often resulting in gene silencing.
What are the 4 distinct mechanisms that can produce an epigenetic form of inheritance in an organism?
- Positive feedback
- Histone modification
- DNA methylation
- Protein aggregation
Define imprinting.
differential expression of a gene allele depending on parental origin; purpose is to control gene dosage - only one allele is expressed as the other allele is imprinted and silenced.
What is the mechanism of silencing in imprinting?
The mechanism of gene silencing is 5-cytosine DNA methylation leading to chromatin condensation.
When a male and female have the same allele silenced and the other one expressed, describe what happens to the offspring.
As the gene goes through the germ cells, the female erases the imprint, while the male imprints both alleles. In normal conditions, the offspring then get one imprinted allele from the father and one expressed allele from the mother. This can go wrong i.e. both are imprinted, leading to disease states.
Describe iron metabolism in cell.
Iron starvation: cytosolic aconitase binds to 5’ UTR region of ferritin receptor. Blocks ferritin (binds iron) translation, and stabilizes mRNA making transferrin (allows iron to come into cell) receptor.
Excess iron: Iron binds to aconitase which leaves UTR, resulting in endonuclease cleavage, allowing ferritin to be made and degraded transferring mRNA.
