Gene expression: Translation Flashcards
What is the triplet codon hypothesis
3 nucleotides specify for one amino acid
How many codons specify for amino acids
61 of 64 codons code for amino acids, remaining 3 are stop codons
What are stop codons
When these are reached in protein synthesis the process stops
What is the role of mRNA
has information for synthesis of proteins from amino acids
What is the role of tRNA
‘Adaptor’ molecule that helps mRNA and amino acids to interact.
How does tRNA bind to amino acids
Specific enzymes have regions that attaches to each molecule and joins them together
What are the two parts of ribosomes
Small and large subunits
What is the purpose of the small subunit of ribosomes
mRNA sits on the small subunit and it then joins with the large subunit.
What is the purpose of the large subunit of ribosomes
Provides areas for the tRNA and amino acids to bind together
What are the regions of the large ribosomal subunit
A is the side where tRNA enters
P is where the growing polypeptides enter
E is where empty tRNA leaves
What are the three stages of translation
Initiation
Elongation
termination
Describe initiation
tRNA binds to the small ribosomal subunit. Identifies 5’ G-cap and attaches to mRNA. The Ribosomal subunit moves along mRNA (5’ to 3’) unit finding initiation codon.
What amino acid is the initial tRNA carrying
first Methionine
What is the initiation codon
AUG - codes for when synthesis of proteins starts.
Describe elongation
The amino acid that is next coded by the mRNA will enter at the A site (attached to it’s tRNA) The initial amino (or growing chain) in P-site transfers to the new one in A-site. Ribosome then moves along mRNA so the new amino acid chain is in the P-site and the old, now empty, tRNA can exit out the E-site.
