🧬 GENETIC CODE – DEGREE LEVEL EXPLANATION
🔹 1. What is the Genetic Code?
The genetic code is the set of rules by which the information in DNA or RNA sequences is translated into proteins (amino acid sequences).
- A codon is a triplet of nucleotides (e.g., AUG) that codes for one amino acid.
- These codons are read by the ribosome during translation of mRNA.
🔹 2. Historical Background
| Scientist | Contribution |
|---|---|
| George Gamow | Proposed the idea that a 3-letter code (triplet) could encode amino acids. |
| Francis Crick | Proposed the “Adaptor Hypothesis”; also helped prove the triplet nature. |
| Marshall Nirenberg | First to crack the genetic code using synthetic RNA (poly-U → phenylalanine). |
| Har Gobind Khorana | Synthesized defined RNA sequences; helped map many codons. |
| Robert Holley | Worked on structure of tRNA. |
| Severo Ochoa | Synthesized RNA in vitro; shared Nobel with Nirenberg. |
🏆 Nirenberg, Khorana, and Holley won the 1968 Nobel Prize in Physiology/Medicine for deciphering the genetic code.
🔹 3. Features of the Genetic Code
| Feature | Description |
|---|---|
| Triplet Code | 3 nucleotides = 1 codon = 1 amino acid |
| Universal | Same in nearly all organisms (e.g., humans, bacteria) |
| Degenerate | Multiple codons can code for the same amino acid (e.g., 6 for leucine) |
| Non-overlapping | Codons are read one at a time, without overlap |
| Comma-less | No punctuation between codons |
| Start Codon | AUG – Codes for Methionine and starts translation |
| Stop Codons | UAA, UAG, UGA – Do not code for any amino acid (terminate translation) |
🔹 4. Codon Table (Genetic Code Chart)
Each codon is a triplet of mRNA bases that corresponds to one amino acid.
Example:
- UUU → Phenylalanine
- AUG → Methionine (Start)
- UAA/UAG/UGA → Stop codons
💻 INTERACTIVE MODEL: Genetic Code Table
Here is a web-based genetic code explorer where users can see codon-to-amino acid mappings dynamically.