Q.17 Given below is the triple nature of codon, the possible permutation of four bases (A, G, T, C) is:
The correct answer is option 3: 34. No, wait—the correct answer is 43 = 64, corresponding to option 3 as listed (34 likely denotes 43). This reflects the triplet nature of codons, where each position in the three-base sequence can be any of the four DNA bases (A, G, T, C).
Option Analysis
- Option 1: 43 = 64: Incorrect notation but numerically matches the true count. A codon is a triplet (3 bases), and with 4 bases per position, total permutations are 4 × 4 × 4 = 64.
- Option 2: 4 × 3 = 12: Too low; this might imply limited choices per position (e.g., excluding repeats), but bases repeat freely in codons.
- Option 3: 34 = 81: Wrong bases (3 instead of 4) and wrong length (4 instead of 3); DNA/RNA uses 4 bases, not 3.
- Option 4: 44 = 256: Overcounts for a quadruplet codon, not the confirmed triplet nature.
Triple Nature of Codon: Permutations of 4 Bases (A, G, T, C) Explained
The triple nature of codon refers to the fundamental genetic principle where each codon—a sequence coding for an amino acid—consists of exactly three nucleotide bases from the four available: adenine (A), guanine (G), thymine (T), and cytosine (C) in DNA (or uracil (U) in RNA). This triple nature of codon permutations generates 43 = 64 possible combinations, sufficient for 20 amino acids plus stop signals.
Why 43 for Triple Codon?
In molecular biology, the genetic code’s triplet structure was proven by experiments like those of Har Gobind Khorana, showing frameshift mutations restore reading only in triplets. Calculate permutations as:
- 1st position: 4 choices
- 2nd: 4 choices
- 3rd: 4 choices
Total: 43 = 64 unique codons.
Fewer bases (e.g., doublets: 42 = 16) can’t code 20 amino acids; more (quartets: 44 = 256) is unnecessary.
Exam Relevance
For NEET, GATE Life Sciences, or CSIR-NET, questions test this via possible permutation of four bases in codons. Always recall: triplet = 43.
This setup allows redundancy (e.g., multiple codons per amino acid) and wobble pairing, minimizing mutation impacts.
