Question

Even before the structure of DNA was solved, studies indicated that the genetic material must have the following properties:

• be able to store information;

• be faithfully replicated and be passed on from generation to generation; and

• allow for changes, and thus evolution, to occur.  

1: Explain how the structure of the double helix showed that DNA had these properties. Write one or two sentences per point.

2:Linus Pauling's model was wrong because it didn't ?

3: he tried to build the structure with what information?

Answer 1

Ans. 1)

• DNA stores genetic information in the sequence of four bases that store information: adenine(A), thymine(T), cytosine(C), guanine(G). They carry instruction that helps to build a living organism. The order of bases is organized into genes and each gene contains specific information for making a functional product.
• DNA can be faithfully replicated and the information can be passed from generation to generation because of its accurate complementary base-pairing rules. The process of DNA replication includes a proofreading mechanism in which the enzyme helicase breaks the hydrogen bond which holds the 2 strands of DNA together and once the two strands are separated they act as a template for the production of the opposite strand.
• DNA is a dynamic molecule as it keeps changing through the process of mutation. Mutations are of 2 kinds- Somatic and germline. The somatic mutation occurs in non-reproductive cells whereas germline mutation occurs in gametes. The germ-line mutation is passed to the organism's progeny. Thus it allows for changes and evolution to occur.

In order to read more about mutation you can refer this link: https://www.nature.com/scitable/topicpage/dna-is-constantly-changing-through-the-process-6524898/

Ans. 2)

Linus Pauling's DNA model was triple-stranded with unionized phosphate groups in the middle holding the molecule together. This model was wrong because if the phosphate groups still had hydrogens, DNA would not be an acid, which it is. Although it was wrong this model served as a catalyst for the development of Watson and Crick model.

Ans. 3)

Linus Pauling found out and hypothesized the structure of guanine as a base ring. He also hypothesized DNA is helical in shape with base groups facing out and a phosphate group at the core. Although his model failed but it was an important discovery which led to the development of Watson and crick model.

Please refer this link for detailed knowledge about Linus Pauling's discovery: https://paulingblog.wordpress.com/2009/04/28/the-pauling-corey-structure-of-dna/#:~:text=Linus%20Pauling%20played%20around%20with,good%20photographs%20of%20nucleic%20acids.