5 Control of Gene Expression Flashcards
what are housekeeping (constitutive) genes?
-genes expressed in all cells because the provide basic functions needed for sustenance of all cells
what are global regulatory mechanisms?
functions which effect the expression of many genes, not specific for a given gene
what basic chemistry allows histones to associate with DNA?
Histones are very basic and therefore very positive. DNA is negative and therefore is attracted to it in its unmodified form.
what is heterochromatin?
trasncriptionally inactvie and not accessible to limiting amounts of DNase1
what is euchromatin?
transcriptionally active and accessible to limiting amounts of DNase1
what are hypersensitivity sites?
sections of chromatin (usually in control regions) that are very sensitive to DNase1
what is a locus control region?
a region of DNA that regulates chromatin organization over a large area of the chromsome
what is the function of SWI-SNF?
it is a nucleosome remodeling protein which can alter chromatin structure. Makes the chromatin more available for protein binding
where does acetylation of chromosomes happen and what does it do?
- happens on lysine residues (very basic and positive residues)
- leads to unfolding and an increase in availability
what sort of activity do many trasncriptional activators possess?
histone acetyltransferase (HAT) activity
what activity do many transcriptional repressors possess?
histone deacetylases (HDAC)
what does hypermethylation in promoter regions lead to?
-diminished gene expression
what does hypomethylation at promoter sites lead to
typically more active transcription
what is CpG methylation a key mediator of?
X inactivation (lyonization) and other epigenetic effects
what is the job of DNA methyltransferase?
adds a methyl group to the 5th carbon atom of some, but not all, cytosine residues in CpG dinucleotides
T/F CpG sequences are hotspots for mutations
True - deamination of 5 methyl cytosine
deamination of 5 methyl cytosine produces what?
thymine, a change that is not noted by repair machiney, leading to mutations
where are CpG islands found? are they actively transcribed?
- found in promoter regions
- yes
CpG regions are usually hypermethylated T/F?
False, they are hypomethylated regardless of whether the gene is active or not
in what regions of the genome are genes typically induced?
interaction at promoter and enhancer sequences
what is the basic process by which heat shock proteins are trasncribed?
cells are heated to a certain temperature which activte heat shock factors, these factors bind to the promoter of heat shock proteins and transcription is allowed to being. this process is induced by heat
what happens in the cytoplasm before steroid hormones induce gene trasncription?
steroids diffuse into the cell, deactivate and inhibitor (bind to intracellular steroid receptors - which are site specific DNA binding molecules), are sent to the nucleus to interact with enhancers which then activate the gene by casuing new interactions at the promoter
on a very basic level, what are DNA microarrays used for?
to determine diferences in the mRNA population between two cell types
mRNA is used to directly bind complimentary oligos on DNA microarrays. T/F
False
-the mRNA of interested in reverse transcribed into cDNA which is then annealed to its complimentary oligos on the DNA microarray
what is the advantage of RNA seq to DNA microarrays
RNA seq is more easily quantifiable
what is the overall purpose of siRNA?
to destroy mRNA of a specific gene within the cytoplasm in order to reduced translation of that gene.
recite the steps in RNA interference with siRNA?
- siRNA engineered to compliment RNA sequence you intend to know down (with a 2-3 nucleotide overhang)
- SiRNA associates with the RISC (RNA induced silencing complex) complex
- RISC is activated by ATP
- RISC splits the ds siRNA into a single strand
- single strand binds to its complimentary mRNA (of interest)
- RISC complex cleaves the complimentary RNA strand
