Genetic Code and Protein Synthesis

Genetic Code

• Definition: Genetic code is the set of instructions in a gene that directs the synthesis of a specific protein.

• Key Codons:

• Example Codons (for amino acids):

  • CAA = Glutamine

  • AUG = Start codon

  • UAA, UAG, UGA = Stop codons

• Characteristics of the Genetic Code:

• Universal: Present in nearly all organisms.

• Unambiguous: Each codon corresponds to a single amino acid.

• Redundant: Multiple codons can code for the same amino acid.

• Precise: Each codon has a specific meaning.

• Degenerate: Some amino acids can be specified by more than one codon (e.g., GCA, GCC, GCG, GCU all code for Alanine).

• Stages of Protein Synthesis:

1. Initiation: Ribosomal subunits attach to the mRNA.

2. Elongation: The ribosome moves along mRNA and links amino acids into a polypeptide chain.

3. Termination: The ribosome reaches a stop codon (UAA, UAG, UGA), ending protein synthesis and releasing the new protein.