Archibald Garrod
- studied alkaptonuria
- the accumulation of homgentisic acid
- discovered the connection between genes and enzymes
Beadle and Tatum
- one gene one enzyme theory
- can only grow when there is AA supplements so there is clearly something wrong with AA synthesis
- add amino acids till you find out which one
mutations in genes
everything before the mutation will not grow but everything after will
where is the amino acid binding site at the tRNA
3’ ACC end
what makes up ribosomes
rRNA and protein
how many ribosomes to make thousands of proteins
one
adaptor hypothesis
position of AA on polypeptide chain is determined by the binding of mRNA and tRNA
Aminoacylaton: Charging tRNA
- tRNA must be bound to their AA
- occurs by enzymes called aminoacyl tRNA synthetases
1. specific synthetases bind to specific AA and ATP is activated
2. 2 phosphates fall off and this ATP turns to AMP. These AMP attach to aminoacyl tRNA synthetases
3. the tRNA will attach to this enzyme and the AA will become attached to the tRNA. AMP is released
4. Once tRNA is charged it gets released
how many tRNAs exist in the cell?
min 20, max 64
isoacceptor tRNA
a tRNA that only recognizes/accepts one AA
differences in translation Euk and Prok
Euk: tRNA is the initiator, has consensus sequence
Prok: has initiation factors, has shine-dalgarno sequence
polyribosomes
translation process can be repeated several times for a single mRNA. Multiple ribosomes for one mRNA
shine-dalgarno sequence
serves as a ribosome binding site for mRNA
Termination in bacteria
tRNA in P site contains completed polypeptide. Binding of release factor the A site breaks bond between polypeptide and tRNA. Ribosomal subunits, mRNA, and RF dissociate
