Question:

The result of the following reaction/experiment carried out by Avery et. al. on Streptococcus pneumonia has proved conclusively that DNA is the genetic material;

Updated On: Feb 23, 2024
  • Live 'R' strain + DNA from 'S' strain + DNAase
  • Heat killed 'R' strain + DNA from 'S' strain + DNAase
  • Live 'R' strain + DNA from 'S' strain + RNAase
  • Live 'R' strain + Denatured DNA of'S' strain + protease
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The Correct Option is A

Solution and Explanation

R-strain is rough and harmless, while S-strain is the smooth and virulent form of Streptococcuspneumoniae. In their experiment, Avery et al., found out that only when DNA from S-type bacteria is added to a culture of R-type bacteria, R-type gets converted to S-type strain. This transformation of R into S-type did not occur on addition of carbohydrate or protein from S-type bacteria. Moreover, in the first scenario, if DNase enzyme was added, i.e., Live 'R' strain + DNA from 'S' strain + DNase, the transformation would not have occurred, proving conclusively that DNA, indeed is the genetic material. Thus, the correct answer is option A.
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Concepts Used:

The Molecular Basis of Inheritance

DNA Replication:

DNA synthesis is commenced at particular points within the DNA strand referred to as ‘origins’, which are certain coding regions. There are numerous origin sites, and when replication of DNA starts, these sites are mentioned as replication forks. Within the replication, the complex is the enzyme DNA Helicase, so that they can be utilized as a template for replication. DNA Primase is another enzyme that's essential in DNA replication.

RNA:

Ribonucleic acid (RNA) is an essential biological macromolecule that exists all together in biological cells. It is principally involved in the synthesis of proteins, that carry the messenger instructions from DNA, which itself contains the genetic instructions needed for the event and maintenance of life. In some viruses, RNA, in spite of DNA, carries genetic information.

Genetic Code:

Genetic code is the term we use in the manner that the four bases of DNA--the A, C, G, and Ts--are strung together in a way that the ribosome, the cellular machinery, can read them and switch them into a protein. In the ordering, every three nucleotides during a row count as a triplet and code for one amino alkanoic acid.

Read More: Molecular Basis of Inheritance