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mol. genetics ch 21
translation
| Question | Answer |
|---|---|
| what is translation and how does it happen? | translation is the coding of mRNA into a polypeptide/protein |
| what makes up a ribosome? | two subunits that have specific roles in translation |
| how many ribosomal subunits are there? | two subunits |
| what is tRNA? | small RNA molecules that translates the genetic code from mRNA to proteins |
| what is the difference between a charged and uncharged tRNA? | charged tRNA has an amino acid attached to it, while an uncharged tRNA does not. |
| what are the different sites within a ribosome? | A site, P site, anf E site |
| what happens at each ribosomal site? | A- an aminoacyl tRNA enters this site; P- peptidyl tRNA is bound in this site; E- deacylated tRNA exits this site |
| what is translocation? | the expelling of the uncharged tRNA from the P site, allowing the new peptidyl-tRNA to enter |
| what are the three stages of translocation? | expulsion of uncharged tRNA from P site which allows near peptidyl tRNA to enter, entry of the aminoacyl-tRNA at the A site, |
| what size are prokaryotic ribosomes? | 70S total |
| what size are ribosomal subunits? | 50S and 30S |
| what are the prokaryotic initiation factors and what do they do? | they are proteins responsible for facilitating the entry of mRNA and tRNA into the initiation complex |
| what is the prokaryotic initiator tRNA and what amino acid does it carry? | it is the aminoacyl-tRNA that initiates bacterial polypeptide translation; and it carries formylmethionine |
| how does a prokaryotic ribosome find the initiation binding site? | through a direct, base-pairing interaction between the ribosome and a specific sequence located just before the start codon |
| what is the shine-delgarno sequence? | ribosomal binding site in bacterial mRNA, usually 5'...AGGAGG... 3' |
| what is EF-Tu and what does it do? | it is an elongation factor and it mediates the entry of the aminoacyl-tRNA into the A site |
| what sizes are eukaryotic ribosomes and what size are their subunits? | 80S total; subunits are 60S and 40S |
| how does a eukaryotic ribosome find its start site? | the 40S subunit scans the mRNA from the 5' end in a linear process until it encounters the AUG initiation codon |
| how is eu. ribosome finding its start site different than a prokaryotic ribosome? | in eukaryotes, small subunits recognize the 5' cap and move to the initiation site, where they join larger subunits. in prokaryotes, small subunits bind directly to the initiation site |
| what roles do eukaryotic initiation factors play in ribosome binding? | they facilitate the formation of an initiation complex with the 5' end of the mRNA, binding the mRNA factor complex ot the Met-tRNA-factor complex, and detecting binding of initiator tRNA to AUG at the start site |
| what is peptidyl transferase and where is it located? | it is the activity of the large ribosomal subunit that synthesizes a peptide bond when an amino acid is added to the growing polypeptide chain. it is located within the large ribosomal unit |
| how many total codons are there? | 64 codons |
| what are stop codons? | codons that terminate translation |
| what are release factors? | proteins that terminate translation through recognition of the stop codon, and catalyzing the release of the polypeptide from the ribosome |
Created by:
angievelasco