Question

Which of the following correctly represents hydrogen bonded pairs in DNA?

• A. $G = C$ ; $T \equiv A$
• B. $G \equiv T$ ; $A = C$
• C. $G = A$ ; $T \equiv C$
• D. $G \equiv C$ ; $T = A$

Hint:

Base Pairing in DNA.

• G $\equiv$ C: Three hydrogen bonds.
• T = A: Two hydrogen bonds.
• This ensures specificity and stability in the double-stranded DNA structure.

Answer 1

The Correct Option is D

DNA consists of two complementary strands held together by hydrogen bonds between nitrogenous bases:

• Guanine (G) forms three hydrogen bonds with Cytosine (C) → represented as G $\equiv$ C.
• Thymine (T) forms two hydrogen bonds with Adenine (A) → represented as T = A.

This specific and complementary pairing ensures the double helix structure of DNA is stable.

Answer 2

Step 1: Understand hydrogen bonding in DNA base pairs
DNA structure is stabilized by hydrogen bonds between complementary nitrogenous bases. These base pairs follow Chargaff's rules and specific hydrogen bonding patterns.

Step 2: Hydrogen bonding between Guanine (G) and Cytosine (C)
Guanine pairs with Cytosine via three hydrogen bonds, which is represented as $G \equiv C$. This triple bond makes the G-C pair stronger and more stable.

Step 3: Hydrogen bonding between Thymine (T) and Adenine (A)
Thymine pairs with Adenine through two hydrogen bonds, represented as $T = A$. This double bond is slightly weaker than the G-C pairing.

Step 4: Conclusion
Therefore, the correct representation of hydrogen bonded pairs in DNA is $G \equiv C$ and $T = A$, reflecting the triple and double hydrogen bonds respectively.