Biology Translation

In the genetic code, a codon is a sequence of three nucleotides on an mRNA molecule that corresponds to a single specific amino acid in a polypeptide chain. This triplet code ensures that the genetic information is translated accurately.

Translation is terminated when the ribosome encounters a stop codon (UAA, UAG, or UGA) on the mRNA strand. Since there are no tRNAs with anticodons complementary to stop codons, release factors bind instead, causing the polypeptide chain to be released.

After a peptide bond is formed between the amino acids, translocation occurs, meaning the ribosome moves along the mRNA by one codon. This movement shifts the now-empty tRNA into the exit (E) site, allowing it to detach and leave the ribosome.

When two tRNA molecules are bound to adjacent codons on the mRNA within the ribosome, the amino acids they carry are positioned close together. An enzyme in the ribosome then catalyzes the formation of a peptide bond between these amino acids to grow the polypeptide chain.

Once the initiator tRNA binds to the start codon, the next codon is exposed in the A site of the ribosome. The complementary anticodon of a second tRNA carrying its specific amino acid then binds to this second mRNA codon.

Translation initiation begins when the small ribosomal subunit binds to the mRNA molecule, followed by the assembly of the complete ribosome. Only after this attachment can the initiator tRNA bind to the start codon.

During translation, the three-nucleotide codons on the mRNA pair with complementary three-nucleotide anticodons on the tRNA molecules. This base-pairing ensures that the correct amino acid is added to the growing polypeptide chain.

Transfer RNA (tRNA) molecules function as adaptors that carry specific amino acids to the ribosome, matching them to the appropriate codons on the mRNA template. They do not synthesize amino acids or form peptide bonds themselves.

Translation is the process where the genetic code carried by mRNA is decoded to synthesize a specific polypeptide chain (protein). Transcription, not translation, is the process where mRNA is created from DNA.

In eukaryotic cells, translation occurs in the cytoplasm (either free-floating or on the rough endoplasmic reticulum) where ribosomes are located. Transcription, on the other hand, occurs in the nucleus.