Translation

• Universal: All organisms follow the same genetic code.
• Degenerate: Many amino acids have more than 1 codon.
• Unambiguous: A codon can only code for one specific amino acid.
• A codon is a sequence of three bases in mRNA that codes for specific amino acids and controls the start and termination of translation.
• Translation is the conversion of the genetic information encoded in RNA into the amino acid sequence of a protein in 3 steps: (initiation, elongation, termination).
• Translation in prokaryotic cells occurs on ribosomes that are present in the cytoplasm. Translation in eukaryotic cells occurs on ribosomes that are present in the cytoplasm or on the rough endoplasmic reticulum.
• • The mRNA attaches to the ribosome. Translation is initiated when the rRNA in the ribosome interacts with the mRNA at the start codon.
• • The sequence of nucleotides on the mRNA is read in triplets called codons. The first exposed codon of the mRNA is always AUG. A tRNA with the complementary anticodon UAC forms hydrogen bonds with the codon. This tRNA has the amino acid methionine attached.
• • The anticodon of a second tRNA bonds with the next codon on the mRNA molecule. This tRNA brings in a new amino acid.
• • A peptide bond is formed between the two amino acids. The reaction is catalyzed by an enzyme in the small ribosomal subunit known as peptidyl transferase.
• • The ribosome will then move along the mRNA to read the next codon. A new transfer RNA brings in a new amino acid, which joins the second one. The first tRNA leaves.
• • The polypeptide chain continues to grow until a stop codon in the mRNA is read. Translation stops.
• The template strand is the strand of DNA to which RNA polymerase attaches to attach complementary bases during transcription. The template strand is also known as the non-coding strand.
• The non-template strand is also known as the coding strand. When referring to DNA transcription, the coding strand is the DNA strand whose base sequence corresponds to the base sequence of the mRNA produced, although with thymine replaced by uracil.