Adenine in DNA structure pairs with?

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2016

Explanation

In DNA, base pairing is highly specific due to the chemical structures of the bases.
Adenine (A), which is a purine, forms a complementary pair with Thymine (T), which is a pyrimidine.
This A-T pairing is stabilized by two hydrogen bonds, which hold the two strands of the DNA double helix together.
This principle is known as Chargaff's rule, which states that the amount of Adenine equals Thymine, and Guanine equals Cytosine.

Option B: Cytosine (C) is a pyrimidine base that pairs with Guanine (G), not Adenine.
Option C: Guanine (G) is a purine base that pairs with Cytosine (C), not Adenine.
Option D: Pyrimidine is a class of nitrogenous bases (including Cytosine and Thymine), not a specific base. While Adenine pairs with a pyrimidine (Thymine), this answer is too general and not the specific partner.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain DNA structure and complementary base pairing as background academic context rather than a clinical decision trigger.
Understanding DNA base pairing is fundamental to genetics and molecular biology. The sequence of these base pairs forms the genetic code that dictates all cellular functions.
Errors in base pairing during DNA replication can lead to mutations, which may cause genetic disorders or contribute to the development of cancers.
Many diagnostic and therapeutic techniques, such as Polymerase Chain Reaction (PCR) for detecting infectious agents or genetic diseases, and certain anticancer drugs, rely on the principles of DNA base pairing.

How to Approach the Question

First, identify the core concept of the question, which is DNA base pairing.
Recall the fundamental rules of complementary base pairing in DNA: Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C).
A useful mnemonic is 'At The Golf Course' (A-T, G-C).
Evaluate the options based on this rule. Adenine pairs with Thymine.
Eliminate the other options: Cytosine pairs with Guanine, Guanine pairs with Cytosine, and Pyrimidine is a category, not a specific base.

Concept Tested & Keywords

QNoGju-8QfAh26ukYtxRpc

E6 Biochemistry U Satyanarayana— Part 1 (pp 26-420 of 840) pp. 63-65, 61-63

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart A (pp 1-239 of 478) p. 216-218

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