Recombinant DNA Technology, Transgenic Crops, Gene Editing and PPV&FRA/IPR

Functional Components of a Bacterial Operon:

• Promoter $\rightarrow$ (IV). Binding site for RNA polymerase: The DNA sequence upstream of the transcription initiation site where RNA polymerase holoenzyme recognizes and binds to begin transcription.
• Operator $\rightarrow$ (II). Site where repressor binds: The regulatory DNA segment situated between the promoter and structural genes that physically interacts with the repressor protein to block or permit RNA polymerase transit.
• Structural gene $\rightarrow$ (III). Code for functional proteins: The cistronic reading frames (lacZ, lacY, lacA) that transcribe polycistronic mRNA translating into functional enzymes.
• Regulatory gene (lacI) $\rightarrow$ (I). Produces repressor protein: Constitutively transcribed gene encoding the lac repressor protein.

Matching sequence: (A) - (IV), (B) - (II), (C) - (III), (D) - (I).
Correct Answer: Option 1.

Replication Origin and Okazaki Fragment Synthesis:

• Statement (I) is FALSE: Prokaryotic circular chromosomes (e.g., E. coli) initiate DNA replication from a single, unique origin of replication (designated as oriC), NOT from multiple origins. Multiple origins of replication (ARS elements) are an exclusive hallmark of large eukaryotic linear chromosomes.
• Statement (II) is FALSE: Okazaki fragments are synthesized exclusively on the lagging strand due to the 5' $\rightarrow$ 3' catalytic limitation of DNA polymerase and antiparallel template orientation. The leading strand is synthesized continuously as a single unbroken strand.

• Rosalind Franklin provided the critical X-ray diffraction data (notably 'Photograph 51') that revealed the helical nature, phosphate backbone on the outside, and dimensional parameters of B-DNA.
• Franklin passed away tragically from ovarian cancer in April 1958 at the age of 37.
• James Watson, Francis Crick, and Maurice Wilkins were awarded the Nobel Prize in Physiology or Medicine in 1962.
• Under the statutes of the Nobel Foundation established in 1974 (and traditionally honored prior), Nobel Prizes are not awarded posthumously (after a nominee's death).
• Therefore, the reason she was not awarded was that she died before the Nobel award was conferred (Option 4).

• 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).