Ribosomal & Transfer RNA

Ribosomal RNA (rRNA) A ribosome is roughly 50% protein and 50% RNA (known as rRNA).
Transfer RNA (tRNA)
• tRNA is found in large amounts in the cytoplasm.
• Single stranded but folded back on itself with three exposed bases (‘anticodon’) at one end and a particular amino acid at the opposite end.
• tRNAs are ‘adapters’ linking amino acids to nucleic acids in protein synthesis.
• There are 64 (4 x 4 x 4) possible triplets;
• there are 61 tRNAs - the other 3 are ‘stop’ signals
• There are only 20 different amino-acids, so

• Each amino-acid is coded for by more than one codon (tRNA);
• Thus the code is degenerate (or ‘semi-redundant’)

Note: transcription occurs in the nucleus; translation occurs in the cytoplasm.

CYTOPLASM