Prokaryotic and Eukaryotic Gene Regulation
I've got so many Operons to regulate ____? What am I?
What is gene expression, and who is a Prokaryote?
Does splicing happen in the nucleus or cytoplasm?
What is the nucleus?
What binds to my consensus sequence/promoter?
What is a 30s ribosome subunit?
My mRNA undergoes splicing. What am I?
Who is a Eukaryote?
I'm an inducer; define me.
What is a small molecule that inactivates a repressor to allow transcription
(e.g., allolactose in the lac operon:
Allolactose binds LacI, lifting negative control so RNA polymerase can proceed.)
Why isn’t a fresh eukaryotic transcript functional yet?
What is it’s a primary transcript that needs processing (5′ cap, splicing, 3′ poly-A)?
(Pre-mRNA requires modifications before translation.)
My bacterial mRNA says AUG—what does tRNA bring, and what’s its anticodon?
What is methionine (fMet in bacteria) and anticodon UAC?
What binds to my consensus sequence/promoter?
What is an RNA polymerase (specifically sigma 70 in prokaryotes)?
Two Nobel laureates made a groundbreaking discovery when investigating E. coli eating sugar. What did they find?
What is the discovery of the operon model?
(Jacob and Monod showed that related genes can be switched on/off together by DNA regulatory sites and proteins, the foundation of gene-regulation logic in bacteria.)
Why can bacteria start translation while still transcribing? (Compare it to Eukaryotes)
What is they don't have a nucleus and lack introns.
There are 61 sense codons but only ~46 tRNAs in E. coli; what principle fixes this? Explain it.
What is wobble base pairing?
(Non-standard pairing at the 3rd codon position allows one tRNA to read multiple codons.)
Where does transcription differ from DNA replication? (There are many answers I'll take two)
What is the product (DNA copy Vs. section of RNA) and igitation (Primer, no primer)
Two foods, one choice. With glucose and lactose present, what tips the balance?
What are CAP–cAMP levels (positive control) and LacI repression (negative control)
(Low cAMP with glucose prevents CAP activation; the operon is only fully on when lactose is present and cAMP is high.)
Prokaryotic rRNA operon logic: 5S, 16S, 23S are transcribed how?
What is together from a single promoter, then processed into mature rRNAs?
(One precursor is cleaved and modified.)
Why does ‘degenerate code’ not mean ‘ambiguous code’?
What is multiple codons can specify one amino acid (degenerate), but each codon specifies only one amino acid (not ambiguous)?
What's the purpose of an Operon?
What is to control gene expression inaccordance to the environment?
(Longer version: What is to coordinate and regulate the transcription of several functionally related genes from a single promoter/operator as one mRNA, enabling rapid, energy-efficient responses to environmental changes?)
Classify lac and trp by control type(s) and explain.
What is lac = negative inducible and positive inducible; trp = negative repressible?
Lac needs inducer (allolactose) and CAP–cAMP; trp uses a corepressor (tryptophan) to turn off.
What's so great about alternative splicing? (Hint: Why does it allow organisms with less DNA express more complex phenotypes?)
What is it increases protein diversity from one gene, helping explain complexity without larger gene counts?
(Different exon combinations yield multiple isoforms.
Isoform = protein variant from one gene)
Explain the steps to translation.
What are initiation, elongation, and termination: (initiation) 30S subunit + initiator tRNA-fMet bind the Shine–Dalgarno sequence and AUG, then 50S joins; (elongation) codon recognition, peptide-bond formation and translocation; (termination) "via" stop codon?
What's the role of an operator? Consider its location in the operon.
What is the operator is a regulatory site bound by repressor/activator proteins?
(Lac I repressor protein binds downstream of the promoter to stop transcription.)