15. Rank the following ideas/discoveries from oldest to most recent.
(I) DNA is the molecule responsible for heredity
(II) Living things best suited to their environment are more likely to survive, reproduce
and pass their characteristics to future generations
(III) The molecular structure of DNA corresponds to a double helix
(IV) Different pairs of alleles are passed onto the offspring independently of each other
a. I, II, III, IV
b. IV, II, I, III
c. II, IV, I, III
d. II, I, III, IV
The correct sequence ranks these foundational genetics and evolution concepts chronologically for CSIR NET Life Sciences preparation. Option c. II, IV, I, III provides the accurate order from oldest to most recent discovery.
Chronological Order
Natural selection (II), proposed by Charles Darwin, appeared in On the Origin of Species published on November 24, 1859, describing how suited organisms survive and pass traits to offspring. Gregor Mendel’s law of independent assortment (IV), from pea plant experiments, stated alleles separate independently during gamete formation and was published in 1866. DNA as the hereditary molecule (I) gained confirmation through Avery, MacLeod, and McCarty’s 1944 bacterial transformation experiments. The DNA double helix structure (III) was elucidated by Watson and Crick in their April 1953 Nature paper.
Option Analysis
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a. I, II, III, IV: Incorrect; places DNA heredity (1944) before natural selection (1859) and independent assortment (1866).
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b. IV, II, I, III: Wrong; independent assortment (1866) precedes natural selection (1859).
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c. II, IV, I, III: Correct; follows 1859 (II), 1866 (IV), 1944 (I), 1953 (III).
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d. II, I, III, IV: Incorrect; DNA heredity (1944) before double helix (1953), but independent assortment (1866) misplaced after 1944.
Exam Relevance
This question tests historical milestones in inheritance biology (CSIR NET Unit 8), linking Darwin’s evolution, Mendel’s genetics, Avery’s molecular proof, and Watson-Crick’s structure. Mastering timelines aids PYQ solving and conceptual clarity for competitive exams.
