Information flow in cells Flashcards
What is the definition of translation.
Process in which the nucleotide sequence of a mRNA is used to order and join amino acids into a polypeptide chain
What is the start codon and what amino acid does it code for?
AUG - Methionine
What are the three termination codons?
UAA
UAG
UGA
What are the characteristics of genetic code?
Specific
Universal
Redundant/degenerate
Non-overlapping
What is a reading frame?
Sequence of codons that runs from a start codon to a stop codon
What determines the reading frame for a mRNA?
The AUG start codon encoding methionine
How many tRNAs are in humans?
50
How are amino acids attached to their cognate tRNAs?
Specific aminoacyl-tRNA synthetase
What bond links the amino acids to the tRNAs?
High-energy ester bond
Where are amino acids linked to tRNA?
Linked to the 3’ end of tRNA via the free 2’ or 3’ -OH of adenylate and involving ATP hydrolysis
How can we describe the binding of the tRNA anticodon to the mRNA?
Complementary and antiparallel
What is the catalyst for the formation of peptide bonds between amino acids?
RNA
What are the three steps in translation?
Initiation
Elongation
Termination
What is the initiation site of translation for prokaryotes?
Shine-Dalgarno sequence
What is the initiation site of translation for eukaryotes?
Kozak box - (GCC)RCCAUGG
R - purine
What are the steps in initiation of translation?
Small ribosomal subunit binds underneath
Met-tRNA binds to start codon
Large ribosomal subunit binds above completing the initiation complex
How does elongation occur in translation?
Aminoacyl-tRNA enter
Met-tRNA and next tRNA adjacent to each other and peptidyl transferase forms a peptide bond between them
Ribosome translocates, ejecting uncharged tRNA
Process repeats
How does termination occur in translation?
Release factor binds to codon
Hydrolysis of the ester linkage
Disassembly of ribosome
What is the polysome?
mRNA and many ribosomes
How does the cell translate protein rapidly and maximise the life of the mRNA?
Rapid recycling of ribosomes
Load more than 1 ribosome onto an mRNA
How does streptomycin and other aminoglycosides work?
Inhibit initiation and cause misreading of mRNA in prokaryotes
