Molecular Basis of Inheritance
Nucleic acids are long polymers of nucleotides. While DNA stores genetic information, RNA mostly helps in transfer and expression of information. DNA, being chemically and structurally more stable, is a better genetic material. However, RNA is thought to have evolved first. DNA replicates semiconservatively. During transcription, one strand of DNA acts as template to direct the synthesis of complementary RNA. The genetic code is read again on the principle of complementarity by tRNA, which acts as an adapter molecule. Protein synthesis is done by ribosomes. Both transcription and translation are energetically very expensive processes. Regulation of gene expression refers to a very broad term that may occur at various levels. The genes in a cell are expressed to perform a particular function or a set of functions. Human Genome Project was a mega project that aimed to sequence every base in human genome. Many new areas and avenues have opened up as a consequence of the project.
The biochemical characterisation of transforming principle was proved by -
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Avery, Macleod and McCarty
Griffith showed that something from the dead S cells could change living R cells, and he called it the transforming principle. He did not find out what it was. The biochemical nature of the principle was worked out by the next set of scientists.
(1) Frederick Griffith — Incorrect. He showed transformation, but the chemical nature of the principle was not defined by his experiments.
(2) Avery, Macleod and McCarty — Correct. They purified proteins, DNA and RNA from the heat-killed S cells and tested which one could transform R cells. In this way they showed that DNA is the transforming principle.
(3) Alfred Hershey and Martha Chase — Incorrect. Their phage experiment later settled that DNA is the genetic material.
(4) Meselson and Stahl — Incorrect. They worked on the replication of DNA, not on the transforming principle.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
The Search for Genetic Material – …
