| A | B |
|---|
| mRNA | Pol II, encodes polypeptide sequence, lowest abundance |
| rRNA | Pol I, components of ribosomes, Highest relative abundance |
| tRNA | Pol III, moderate relative abundance, aa carriers, splicing ribosomes |
| rRNAs form | intense bands on gel because they make up 90% of total RNA. |
| small RNA | tRNAs, numbers equivelant to rRNA |
| small RNAs | form a faint band at bottom of gel because it has much less mass. |
| mRNA on gel | looks like a background smear because there are so many that the bands blend together |
| Promoter | region of DNA used to activate or repress transcription |
| minimal promoter | smallest region of promoter that drives detectable transcription |
| Enhancer | regulates transcription like a promoter, but can be moved relative to the gene it controls. |
| Enhancer | that its 5'-3' orientation can be flipped in a transgenic expression assay |
| Enhancer | often located great distances from their genes |
| TATA Box | found in pol II minimal promoters |
| minimal promoter | priming transcription. Needs upstream sequences of enhancers for elevation or repression of translation. |
| Minimal Promoter | drive constitutive, low level transcription. Not responsible for regulation. |
| Initiation Complex | cluster of proteins assemble around a promoter and attracts RNA Polymerase |
| TBP | Binds TATA |
| TAFs | assemble around TBP to form initiation complex at minimal promoter |
| Start of Transcription | usually a purine (A>G), 26-34 bp downstream of TATA box. general starter is GTTGCTCCTG/AAC |
| Mechanism of Action | TBP binds a TATA box. TAFs are then recruited to form a core initiation complex. This complex attracts an RNA polymerase which “looks” for a purine about 30 bp downstream, where it will initiate transcription. |
| Promoters and enhancers are | clusters of recognition sequences bound by transcription factors |
| Transcription Factors | protein that binds recognition sequences to control transcription |
| DNA binding Domain | a region of transcription factors that recognizes and binds specific sequences of DNA |
| Primary Transcript | RNAs that have not been processed |
| Capping | Gunosine is added to the first nucleotide of the primary transcript by an unusual 5'- 5' bond |
| cap is methylated along with | 2 hydroxyls of1st and 3rd nucleotides |
| capping and methylation is believed to increase | mRNA stability by resisting degradation |
| Splicing | removal of section of primary transcript |
| what is spliced out? | intron |
| what regions are retained? | exons |
| What does the spicing? | spliceosomes |
| snRNPs | made of proteins and snRNAs |
| The enzymatic activity resides in what in snRNPs? | the snRNAs |
| snRNAs are transcribed by what? | Pol III |
| Polyadenylation | add 20-300 adenosines |
| Where does a Poly-A tail get added? | 3' end |
| Polyadenylation is signaled by what? | AAUAAA |
| Polyadenylation continues after its signal for how long? | 500-2000 bps |
| The excess RNA is cleaved at | CA, 10-30 bp downstream of AAUAAA |
| the clipped off RNA fragment is | degraded |
| Replication dependent histones | not spliced and polyadenylated |
