Question

Which of the following is the correct sequence of events in the origin of life?

I.	Formation of protobionts
II.	Synthesis of organic monomers
III.	Synthesis of organic polymers
IV.	Formation of DNA-based genetic systems

• A. II, III, I, IV
• B. II, III, IV, I
• C. I, II, III, IV
• D. I, III, II, IV

Answer 1

Answer: (A)

The primitive reducing atmosphere of earth was rich in water vapour, carbon monoxide, carbon dioxide, nitrogen and hydrogen. UV light, high temperature and lightening served as sources of energy for chemical reactions between above mentioned gases to form simple organic compounds such as sugars, amino acids, fatty acids, glycerols and nucleotides (II). These simple organic compounds were washed from atmosphere to ocean through rain. They served as monomers for formation of complex organic compounds in ocean (III). This was followed by assemblage of organic polymers to form protobionts (I). RNA serves as first genetic material which was then replaced by DNA as later is most stable and less reactive (IV).

Therefore, the correct answer is option A.