Biochemistry · MU Sofia

46. Genetic Code

Explains the genetic code as the set of rules translating nucleotide triplets into amino acids, covering codon features such as redundancy, near-universality, and the start and stop codons. It then sets out how to read a codon from the code table and walks through translation in three stages: initiation, elongation and termination, with the key enzymes and factors. It closes with antibiotic and toxin inhibitors of protein synthesis, grouped by prokaryotic and eukaryotic targets, followed by multiple-choice questions with answers.

Inside: 15 sections · 5 labelled pictures · 10 flashcards · 5 min

Topic 46 of 70 in the MU Sofia syllabus for Biochemistry (Medicine, Year 2). The free AceMed note covers it in 10 sections, about 634 words (5 min of reading), with 10 flashcards.

In this note

  1. Genetic Code
  2. The genetic code matches each mRNA codon with its amino acid or function.
  3. Biosynthesis of Proteins
  4. Overview
  5. Steps:
  6. Key Enzymes and Factors
  7. Inhibitors of Protein Synthesis
  8. Mechanism-Specific Inhibitors
  9. MCQs ☺
  10. Answers

Genetic Code

Definition:

Genetic Code: The set of rules by which the information encoded within genetic material (DNA or RNA) is translated into proteins by living cells.

Genetic Code

Characteristics:

  • Triplet Code: Each amino acid is encoded by a sequence of three nucleotides, called a codon.
  • Redundancy: Multiple codons can encode the same amino acid (e.g., both UUU and UUC code for phenylalanine).
  • Universality: The genetic code is nearly universal among all organisms, from bacteria to humans.
  • Start Codon: AUG, which codes for methionine, also signals the start of protein synthesis.
  • Stop Codons: UAA, UAG, and UGA signal the termination of protein synthesis.

The genetic code matches each mRNA codon with its amino acid or function.

Suppose you want to determine which amino acid is encoded by the CAU codon.

  1. 1 Find the first base, C, in the left column.
  2. 2 Find the second base, A, in the top row. Find the box where these two intersect.
  3. 3 Find the third base, U, in the right column. CAU codes for histidine, abbreviated as His.

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