Who among the following was the first person to account for and measure the nucleotide amounts in DNA in the 1950s?

Appeared in: DSSSB 12 August 2024

Explanation

Erwin Chargaff is credited with the quantitative analysis of DNA's base composition in the late 1940s and early 1950s.
His key finding, known as Chargaff's rules, established that the amount of adenine (A) equals thymine (T) and the amount of guanine (G) equals cytosine (C).
This principle of base pairing (A=T, G=C) was a fundamental clue that helped Watson and Crick deduce the double-helical structure of DNA.
The question specifically asks about measuring nucleotide amounts, which directly points to Chargaff's work.

Option A: Oswald Avery's work focused on identifying the 'transforming principle'. His experiments proved that DNA, not protein, is the substance responsible for carrying genetic information.
Option B: Rosalind Franklin used X-ray crystallography to study the structure of DNA. Her famous 'Photo 51' provided critical evidence for the helical nature of DNA.
Option D: Friedrich Miescher was the first to discover and isolate nucleic acids in 1869, which he called 'nuclein'. However, his work was much earlier, and he did not determine the base composition.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Historical contributions to the discovery of DNA structure as background academic context rather than a clinical decision trigger.
The principle of complementary base pairing (A-T, G-C) discovered by Chargaff is the foundation of modern molecular biology and genetics.
This principle is fundamental to DNA replication, transcription, and repair mechanisms within the cell.
Techniques like the Polymerase Chain Reaction (PCR), used extensively in diagnosing infectious diseases (like COVID-19) and genetic disorders, rely on the specific binding of primers to complementary DNA sequences.

How to Approach the Question

Identify the key actions and timeline in the question: 'measure nucleotide amounts' and '1950s'.
Recall or look for the specific contributions of each scientist listed in the options.
Oswald Avery is associated with proving DNA is the genetic material (1944).
Rosalind Franklin is known for X-ray crystallography of DNA (early 1950s).
Friedrich Miescher discovered nucleic acids much earlier (1869).
Erwin Chargaff's work directly involved quantifying the bases and establishing the A=T, G=C rule around 1950. This matches the question's keywords perfectly.

Concept Tested & Keywords

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E6 Biochemistry U Satyanarayana— Part 1 (pp 26-420 of 840) p. 63-65

E6 Harper's Illustrated Biochemistry2023 (pp 26-793 of 813) p. 333-335

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