Match List I with List II

List I		List II
A	Frederick Griffith	I	Genetic code
B	Francois Jacob & Jacque	II	Semi-conservative mode of DNA replication
C	Har Gobind Khoran	III	Transformation
D	Meselson & Stahl	IV	Lac operon

Choose the correct answer from the options given below:

The correct answer is A-III, B-IV, C-I, D-II.

Let us match the scientific contributors in List I with their corresponding discoveries or concepts in List II:

A. Frederick Griffith (III - Transformation):
In 1928, Frederick Griffith conducted experiments with Streptococcus pneumoniae (the bacterium that causes pneumonia) in mice. He discovered the "transforming principle," demonstrating that non-virulent rough strains of bacteria could be transformed into virulent smooth strains when mixed with heat-killed smooth bacteria. This process is known as genetic transformation.

B. Francois Jacob & Jacque Monod (IV - Lac operon):
In 1961, French scientists François Jacob and Jacques Monod proposed the Operon model to explain genetic regulation of protein synthesis in bacteria. Specifically, they described the lac operon (lactose operon) in Escherichia coli, showing how genes involved in lactose metabolism are turned on or off in response to environmental cues.

C. Har Gobind Khorana (I - Genetic code):
Har Gobind Khorana, along with Marshall Nirenberg and Robert Holley, played a key role in deciphering the genetic code. Khorana developed chemical methods to synthesize defined sequences of RNA, which helped determine how codons (triplets of nucleotides) translate into specific amino acids during protein synthesis.

D. Meselson & Stahl (II - Semi-conservative mode of DNA replication):
In 1958, Matthew Meselson and Franklin Stahl performed a famous experiment using heavy isotope ¹⁵N and light isotope ¹⁴N in E. coli. Their results experimentally proved that DNA replicates in a semi-conservative manner, meaning each new DNA double helix consists of one parent strand and one newly synthesized strand.

Matching the items accordingly:
- A matches with III
- B matches with IV
- C matches with I
- D matches with II

Thus, the correct combination is A-III, B-IV, C-I, D-II.