Molecular Biology & Biotechnology

• codon is a triplet sequence consisting of 3 consecutive nucleotide positions.
• If there are $N$ different types of available bases/nucleotides, and each of the 3 positions can independently be occupied by any of the $N$ nucleotides (with replacement allowed):
  $$\text{Total triplet codons} = N^3$$
• Given $N = 5$ nucleotides (A, T, G, C, X):
  $$\text{Total codons} = 5^3 = 5 \times 5 \times 5 = 125$$
• For comparison, standard biological systems with 4 bases yield $4^3 = 64$ codons.
• Thus, the number of triplet codons formed is 125 (Option 2).

Statement (I) is correct: In 1962, James Watson, Francis Crick, and Maurice Wilkins jointly received the Nobel Prize in Physiology or Medicine for their discoveries concerning the molecular structure of nucleic acids.
Statement (II) is incorrect: Rosalind Franklin died of ovarian cancer in 1958 at the age of 37, four years before the 1962 award. Under the Nobel Foundation statutes, Nobel Prizes are strictly not awarded posthumously. Her exclusion was primarily due to her death, not merely the maximum 3-person sharing rule.

In molecular biology:
$1\text{ kb (kilobase)} = 1000\text{ base pairs (bp)}$ for double-stranded DNA.

Watson-Crick DNA double helix architecture:

• In double-stranded DNA, the two phosphodiester backbones run equidistant and parallel to each other, but in opposite chemical polarities.
• One strand runs in the $5' \rightarrow 3'$ direction (free $5'$ phosphate to free $3'$ hydroxyl), while the complementary partner runs in the $3' \rightarrow 5'$ direction.
• This antiparallel orientation permits proper hydrogen bonding and steric alignment between complementary purine and pyrimidine base pairs ($A=T$ and $G\equiv C$).