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L34-35: Gene Exp

USCSOM: Biochemistry: L34-35 Gene Expression 2

QuestionAnswer
What do sigma factors do in E. coli? direct E. coli RNA polymerase to categories of promoters; sigma-70
What is highly repetitive DNA? 100,000 - 1,000,000 copies per genome
What is middle repetitive DNA? few - 100,000 copies per genome
Where is highly repetitive DNA found a chromosome? ends of telomeres and centromeres
What is alpha satellite DNA? repetitive centromeric DNA
What does middle repetitive DNA code for? rRNA, tRNA, histones, retrotransposons
What is a retrotransposons? What are the two types? DNA sequence that has the ability to spread and move about via reverse transcriptase; SINES and LINES
What are SINES? short interspersed nuclear elements
What is a common SINES family? What is it related to? a1u1 family; related to 7S RNA coding; 300nt long
What are LINES? long interspersed nuclear elements; codes for a reverse transcriptase
What is a pseudogene? integrated DNA versions of fully processed mRNA; lack introns
Where does gene loss normally occur in humans? only in the RBC
What happens to most cytosine residues that occur in the sequence C-G methylated to give 5-methyl-C
Are expressed genes methylated or unmethylated with respect to 5-methyl-cytosine unmethylated
Methylation of cytosine residues attracts what regulatory enzymes? HDACS that prevent binding from transcription factors
What are HDACs? histone deacetylases
What is a Barr body? inactive X chromosome in females; densly staining; heterochromatic
What are CG islands? unmethylated CG regions in promoter sequences; house-keeping genes
What is does maintenance methylase do? methylates CG of the newly synthesized DNA strand based on the methylation of the parent strand
What is a "cis-acting" DNA element? the nucleotide sequence to which a transcription factor binds
What is a "trans-acting" factor? a protein/transcription factor that binds to a cis-acting sequence
What is HRE? What is its function? hormone response element; activated by receptor-steroid complex to stimulate RNA synthesis
What are the three general classes of proteins that modulate chromatin structure? chromatin remodeling; add/removal of acetyl groups; add/remove modules from histones
What is CREB? a transcription factor that is modified by phosphorylation via PKA/cAMP
What is Pit-1 and function? responsible for transcription of GH and prolactin; autoregulates itself once turned on
Why is PEPCK important for gene regulation? has a very diverse transactivator region upstream from promoter; many physiological inputs will stimulate it
What is variable splicing? splicing of a gene based on pre-mRNA molecules bound in exons; calcitonin is an example
What is polyadenylation? use of a different stopping sites; adding or losing exons; IgM is an example
How is IgM affected by polyadenylation? stimulation leads to upstream poly(A)and secretion where downstream poly(A) anchors the protein to the lipid membrane
Where does RNA editing occur in humans? apolipoprotein B; long apoB-100 in liver and small apoB-48 in small intestine
How does siRNA work? introduction of complementary RNA into cell resulting in silencing of the targeted mRNA; mRNA is "knocked down"
What is miRNA? transcript silencing provoked by endogenous ds RNA; drosha processes these in nucleus
What is RISC? RNAi Silencing Complex; finds mRNA with homology to the 22nt ssRNA and cleaves it
What nucleotides tend to make mRNAs less stable? A and U
What does a "dicer" do? dices long ds RNAs into 21-23 nucleotide fragments
What does Argonaute protein do? removes and degrades ds RNA fragments to create a ssRNA fragment
What enzyme transports Fe in the blood? transferrin
What enzyme stores Fe in the cells? ferritin
How is ferritin mRNA translationally regulated? iron causes IRE (iron responsive element)-BP to lose affinity for mRNA allowing synthesis of ferritin
How is transferring receptor mRNA stability regulated? Fe decreases IRE-BP affinity for mRNA, mRNA is degraded more rapidly reducing Transferring receptor synthesis
What is used as a means to regulate total protein synthesis? phosphorylation of eIF2
How do interferons affect protein synthesis? IFNs induce protein kinase R which phosphorylates eIF2 in presence of dsRNA
How does heme regulate protein synthesis? Heme inhibits heme-regulated kinase so that globin chains are made in presence of heme only
What AAs destabilize proteins? PEST: proline, glutamic acid, Ser, Thr
What protein is known as the "kiss of death" ? Ubiquitin
What is Beta-Thalassemia? decreased lvl or abscence of one or two of the globin chains in hemoglobin
Created by: jlellerm