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MMBIO Quiz 13/14
| Question | Answer |
|---|---|
| stop codons | UAA, UAG, UGA |
| rules for genetic code | each base is a part of one codon. one codon = 3 bases no bases in between codons and no overlapping nearly universal highly degenerate each codon only yields a single type of amino acid |
| how was the genetic code first deciphered? 1. | insertion/deletion revealed genetic code is based on triplet codons |
| how was the genetic code first deciphered? 2. 3 codons known | poly U - UUU = Phe poly A - AAA = Lys poly C - CCC = Pro poly G did not work, triple stranded helix |
| how was the genetic code first deciphered? 3. about 50 codons known | trinucleotide binding assay UUU ribosomes and Phe tRNAs stick, others fall through the filter test all codons to see what they stick to |
| how was the genetic code first deciphered? 4. all 64 codons knwon | repeating codons UCUCUCUCUC --> Leu and Ser over and over AUC AUC AUC AUC --> Ile over and over... |
| wobble hypothesis | sometimes third base in a codon and first base in anticodon can form nonstandard base pair allows some aminoacyl-tRNAs to bind to more than one codon |
| 5' end G C A U I (inonsine - unusual base) | G - U or C C - only G A - only U U - A or G I - U, C, A |
| initiator tRNAs | modified tRNAs - CA mismatch, AU, GGGGGGG modified methionines - have formyl groups added on |
| initiation factors (IFs) | assist to initiate translation |
| IF1 | bind to A site in the ribosome, keeps tRNAs from coming in until ready |
| IF2 | keep 50S and 30S from forming into 70S |
| IF3 | binds to initiator tRNA, hydrolyzes GTP to GDP |
| initiation steps (prokaryotics) | 30S subunit binds to IF1 then IF3, fMet-tRNA comes in with IF2 and base pairs the start codon |
| Shine-Dalgarno sequence | prokaryotes AGGAGG docking site for the ribosome |
| Kozak sequence | eukaryotes GCC A/GCC AUG A helps ribosome find correct AUG start codon |
| translation elongation | mRNA and first aminoacyl tRNA bind to small subunit the aminoacyl tRNA is transferred from the first to second tRNA, the first dissociates cycles repeat until ribosome reaches a stop codon |
| elongation factors (EFs) | help with elongation prokaryotes: EF-Tu, EF1B, EF-G eukaryotes: eEF1A, eEF1B, eEF2 |
| EF-Tu | brings the correct aminoacyl-tRNA to the A site |
| EF-G | moves the ribosome from A P E to make room for next tRNA |
| rRNA - peptidyl transferase activity | catalyzes formation of peptide bonds |
| RFs - release factors | use a tripeptide codon to recognize stop codons and bind |
| RFs (prokaryotes) | RF1: recognizes AUG and UAA RF2: recognizes UGA and UAA RF3:enhaces RF1 and RF2's activity and helps them to exit A site |
| RFs(eukaryotes) | eRF1 recognizes all three stop codons eRF3 catalyzes release with GTP |
| ribosomal recylcing | RRF = ribosomal recycling factor binds to ribosome to break it apart into subunits releases mRNA and tRNA |
| CRISPR - what does it stand for? | clustered regularly interspaced short palindromic sequences |
| CRISPR | bacteria capture small DNA pieces from invading phages and remember that phages are the enemy to later recognize them |
| guide RNA/gRNA | crRNA (shorter) or tracrRNA (longer) complentary to target DNA, guides the Cas9 enzyme |
| Cas9 enzyme | restriction nuclease: cuts at specific sites upstream of PAM sites |
| the guide RNA guides the _____ enzyme to specific sequences | Cas9 |
| CRISPR experiments | kill a gene - knockout introduce a new gene - knockin fix an existing faulty gene |
| dCas9 | dead Cas9 binds and sit on DNA has mutations that inactivate cutting ability stays on DNA - gene OFF fused to activators - gene ON |
| CRISPRa | activation, increases transcription |
| CRISPRi | eleimantes transcription |
| how CRISPR works | pick target DNA design gRNA that matches target Cas9 and gRNA find DNA target Cas9 cuts the DNA upstream of PAM site remove or insert or fix gene |
Created by:
anyasalmon