Which is the correct base pairing found in a normal DNA molecule?

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NDA-I (GAT) Official Paper (Held On: 13 Apr, 2025)
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  1. Adenine pairs with Thymine
  2. Adenine pairs with Guanine
  3. Adenine pairs with Cytosine
  4. Thymine pairs with Guanine

Answer (Detailed Solution Below)

Option 1 : Adenine pairs with Thymine
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Detailed Solution

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CONCEPT:

Base Pairing in DNA

  • DNA (Deoxyribonucleic Acid) is a double-stranded molecule, where the two strands are held together by base pairing between complementary nitrogenous bases.
  • The four nitrogenous bases in DNA are:
    • Adenine (A)
    • Thymine (T)
    • Guanine (G)
    • Cytosine (C)
  • The base pairing follows a specific rule known as Chargaff's Rule:
    • Adenine (A) pairs with Thymine (T) through two hydrogen bonds.
    • Guanine (G) pairs with Cytosine (C) through three hydrogen bonds.

EXPLANATION:

dna

  • Adenine pairs with Thymine - This is correct because adenine always pairs with thymine in a normal DNA molecule.
  • Adenine pairs with Guanine - This is incorrect because adenine never pairs with guanine.
  • Adenine pairs with Cytosine - This is incorrect because adenine never pairs with cytosine.
  • Thymine pairs with Guanine - This is incorrect because thymine never pairs with guanine.

Based on the base pairing rules, the correct answer is: Adenine pairs with Thymine.

Therefore, the correct base pairing found in a normal DNA molecule is that Adenine pairs with Thymine.

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