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Translation (Protein Synthesis)
🧫BiologyPre-Med
Translation is the process by which the information encoded in messenger RNA (mRNA) directs the assembly of amino acids into a protein. It takes place on ribosomes in the cell's cytoplasm, where the mRNA sequence is "read" in codons (three-base units) and translated into a specific sequence of amino acids, forming a polypeptide chain.
- Each set of three mRNA bases (codon) corresponds to one amino acid (according to the genetic code). For example, the codon AUG codes for the amino acid methionine (also serving as the start codon for translation). UAA, UAG, and UGA are stop codons that signal translation to end.
- Translation requires ribosomes (made of rRNA and proteins) and transfer RNAs (tRNAs). tRNAs act as adapters: each tRNA has an anticodon that pairs with a codon on mRNA and carries the appropriate amino acid for that codon. This ensures the amino acids are added in the correct order as the protein is synthesized.
- Translation has three phases: initiation (ribosome assembles at the start codon on mRNA; the first tRNA brings methionine), elongation (the ribosome moves along mRNA, adding amino acids one by one), and termination (when a stop codon is reached, the finished polypeptide is released). Multiple ribosomes can translate a single mRNA simultaneously (forming a polyribosome) to make many copies of a protein.
- If a question asks "Where and how are proteins made from mRNA?" -> the answer is translation, occurring at ribosomes in the cytoplasm, decoding mRNA into amino acids.
- Clues like "codon-anticodon pairing," "ribosome," or "polypeptide chain formation" in a question indicate translation. For instance, a question mentioning tRNA bringing amino acids to match an mRNA sequence is describing the translation process.
- Be prepared for genetic code problems: e.g., given an mRNA sequence and a codon chart, determine the amino acid sequence - that's a direct application of translation (reading codons to find amino acids). Always start at the start codon (AUG) and stop at a stop codon.