Translation Flashcards
What is the function of tRNA
To recognise a specific codon sequence whilst being specific to an amino acid, ensuring a match between the two.
Amino acids are joined to tRNA by an enzyme called aminoacyl-tRNA-synthetases. The RNA world hypothesises that these are either ribozymes or were developed from ribozymes
What is the structure of a tRNA molecule
They are made up of 4 core arms:
Amino acid arm
T arm
Anticodon arm
D arm
There may also be extra arms that vary in size between the T arm and anticodon arm, collectively called the variable loop
What is a reading frame
The sequence of codons from a specific start codon to a stop codon
What is the name and sequence of the start codon
Methionine
AUG
How many stop codons are there and what are there sequences
3
UAA
UGA
UAG
What is the wobble hypothesis
The 3rd base of a codon (1st base of an anticodon) can tolerate more variance than the other two. It means that the same tRNA can identify similar codons and explains the degenerative properties of DNA
What are the exceptions to the universal nature of DNA
Mitochondria contain their own DNA and use a slightly different code
Mitochondria also encode there own tRNAs
Rare amino acids are encoded by special codons
How many possible condones are there and how many specify amino acids
64 possible combinations
61 code for amino acids
3 are stop codons
What is the difference between an eukaryotic ribosome and a prokaryotic one
Prokaryotic ribosome: 70S made up from a 50S subunits and a 30S subunit
Eukaryotic ribosome: 80S made up from a 60S and a 40S ribosome
What are the tRNA binding sites on a ribosome and what do they do
P site: holds the tRNA carrying the amino acid that is growing the peptide chain
A site: holds the tRNA molecule waiting to enter the P site, it contains the next amino acid it the peptide sequence
E site: discharged tRNAs leave through the E site once they have deposited their amino acid
