Translation Flashcards
what types of RNA are involved in translation?
mRNA - messenger
tRNA - transfer
rRNA - ribosomal
what is the role of mRNA , tRNA and rRNA in translation?
- mRNA = template, encodes information to make the protein
- tRNA - carrier, each amino acid brought to mRNA by a specific tRNA
- rRNA - structural and functional roles in ribosomes
4.
what is the start codon on an mRNA?
AUG = methionine= typical 1st codon in protein
at what point on mRNA do we start translating codons?
just after the 5’UTR region - whenever it comes across a start codon
What is an open reading frame?
a set of codons that run continously bounded by an initiation codon and a termination codon = reading frame is determined by which base is chosen as the start of a codon
in protein synthesis usually only one open reading frame contains useful information
is the genetic code universal?
yes - it applies to all species conserved from early stage of evolution
what genetic change causes sickle cell anaemia?
it is due to a missense mutation in the beta globin gene - single nucleotide substitution (a to T) in the codon for amino acid 6 - converts a glutamic acid codon (GAG) to a valine codon (GTG) autosomal recessive
what is the ‘Wobble exception to base pairing’?
wobble = flexible pairings
the wobble base is last 3’ base in codon on mRNA which binds with the first 5’ based in anticodon on tRNA - it allows felxibility/efficiency in use of tRNA - a single tRNA species carrying an AA can recognize 2 codons
so this is why different codons can produce the same AA
what is the role of the ribosome?
they are the factories in which protein synthesis occurs - they are complexes of protein and rRNA - which is extensive secondary structuring stimilar to tRNA -
ribosome brings tRNA and mRNA together to translate nucleotide sequence of mRNA into amino acid of a protein
what are the 2 parts to tranlation initiation?
- assembly of components required for chain formation (tqo ribosomal subunits, mRNA, tRNA specified by the AUG codon, GTP, initiation factors to help ribosome recognise the sequence for the start of translation
- recognition of the start codon by a tRNA methionine molecule
*initiator tRNA is in P site
what are the 3 sites of the ribosome?
- A= aminoacyl site - accepts new tRNA
- P= peptidyl site - contains amino acid chain
- E= exit site - harbours deacylated tRNA on way out of ribosome
describe the process of ‘elongation ‘
elongation involves the addition of amino acids to the carboxyl end of the growing chain - peptide bonds are formed between adjacent amino acids
ribosome moves along mRNA being translated - in 5’ to 3’ direction
- tRNA delivered to A site
- peptide bonds formed
- growing amino acid chain now in A site
- after bond formed, the ribosome is translocated 3 nucleotides to the next codon
describe the process of termination in translation
occurs when one of three termination codons arrives in the A site
stop codon recognized by a release factor
release factor binds to A site which causes the newly synthesized protein to be released and dissasembly of the tRNA - ribosome- mRNA complex
