| Question |
Answer |
| 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 |
Biology Lab Midterm
