Term
| What codons code for the start and stop of translation? What happens when each of those codons are read? |
|
Definition
| AUG codes for methionine which is the start codon for translation. UAA, UAG, UGA are all stop codons which make the polypeptide strand terminate elongation |
|
|
Term
| What is degeneracy/redundancy and why is it important? |
|
Definition
| Degeneracy/redundancy means that almost all amino acids have more than one codon that specifies them. This is important because it allows for mistakes to be made while still maintaining the correct amino acid sequence. This is most commonly seen in the 3rd nucleotide of a codon, also called the wobble position. |
|
|
Term
| silent, nonsense and missense mutations |
|
Definition
| no effect, premature stop codon and a codon that codes for a different amino acid |
|
|
Term
|
Definition
|
|
Term
|
Definition
- main polymerase in transcribing DNA
- binds to the TATA box within the promoter region of the gene
|
|
|
Term
|
Definition
| primary transcript before modifications |
|
|
Term
| What occurs during posttranscriptional processing? |
|
Definition
- splicing: removes introns and ligates exons together
- 5' cap: a 7-methylguanylate triphosphate cap is placed at the 5' end of the transcript
- 3' Poly-A tail: protects end of RNA from degradation
|
|
|
Term
|
Definition
| made up of small nuclear RNAs (snRNA) and small nuclear ribonucleoproteins (snRNPs, 'snurps'); recognizes splice sites and forms lariate that excise the introns |
|
|
Term
| What are the three stages of translation? |
|
Definition
- initiation
- elongation
- termination
|
|
|
Term
|
Definition
- small ribosomal subunit binds to the mRNA (Shine-Dalgarno sequence in prokaryoates, 5' cap in eukaryotes)
- the small ribosomal subunit scans for a start codon
- it lays down N-formylmethionine in prokaryotes and methionine in eukaryotes at the P site
- the large subunit then binds the small subunit
|
|
|
Term
|
Definition
- a new aminoacyl-tRNA is added into the A site
- the growing polypeptide is transferred from the tRNA in the P site to the tRNA in the A site
- the uncharged tRNA pauses in teh E site before exiting the ribosome
- the tRNA in the A site is moved to the P site and it starts over
|
|
|
Term
|
Definition
| occurs when the codon in the A site is a stop codon; release factor places a water molecule on the polypeptide chain and thus releases the protein |
|
|
Term
| posttranslational modifications |
|
Definition
- folding by chaperones
- formation of quaternary structure
- cleavage of proteins or signal sequences
- covalent addition of other biomolecules (phosphorylation, carboxylation, glycosylation, prenylation)
|
|
|
Term
|
Definition
| an inducible or repressible cluster of genes transcribed as a single mRNA |
|
|
Term
|
Definition
| lac operon; bonded to a repressor under normal conditions; they can be turned on by an inducer pulling the repressor from the operator site |
|
|
Term
|
Definition
| trp operon; transcribed under normal conditions; they can be turned off by a corepressor coupling with the repressor and the binding of this complex to the operator site |
|
|
Term
| What are controls on gene expression in eukaryotes? |
|
Definition
- transcription factors: search for promoter and enhancers regions the DNA
- promoters: contain upstream elements that affect how much a gene is transcribed
- enhancers: up or downstream of promoter and amplifies transcription
- histones: acetylated histones allow for easier access to DNA; DNA wrapped in histones can't be accessed
- methylation of DNA: methylation is often linked with silencing gene expression
|
|
|
