Molecular Genetics Translation

-Clover shaped RNA molecule -Transfer RNA -Functions as the delivery system of amino acids to ribosomes as they synthesize proteins -Is very short, only 70-90 base pairs long

-3’ end of tRNA binds to specific amino acids -Anticodon on tRNA complements mRNA codon

-RNA is made in the nucleus -Amino acids float free in the cytoplasm -Enzyme: aminoacyl-tRNA synthetase -An amino acid is attached when needed as this takes energy

-2 subunits: small and large -E site → exit site -P site → polypeptide binding site -A site → amino acid site -Composed of proteins and rRNA -3 tRNA binding sites

-mRNA, tRNA and small ribosomal subunit bind with P site at start codon -Only the first tRNA binds to P at start codon -Large subunit binds using energy from GTP

mRNA read 3 nucleotides at a time in codons -tRNA brings corresponding amino acid into the A site of the ribosome -Ribosome catalyzes dehydration synthesis reaction between amino acids in P site and A site -Peptide bond is formed -Growing polypeptide now attached to tRNA in A site -Ribosome moves forward one codon -Free tRNA in P site exits out the back of ribosome on the E site -tRNA (with polypeptide) moves into P site

-Elongation continues until reaching a stop codon -There is no amino acid for stop codon, just STOP -Release factor binds and hydrolyzes the bond between the last tRNA and its amino acid -New protein is free

• Many ribosomes may simultaneously translate from a single mRNA