Question

The number of Guanines and Adenines present in the DNA molecule of pitch at 170° with 130 Hydrogen bonds between base pairs:

• A. 20, 10
• B. 10, 30
• C. 20, 30
• D. 30, 20

Hint:

Remember, in DNA, guanine and cytosine form 3 hydrogen bonds, and adenine and thymine form 2 hydrogen bonds.

Answer 1

The Correct Option is D

To solve the problem, we need to determine the number of Guanine and Adenine bases present in the DNA molecule at a pitch of 170° with 130 hydrogen bonds between base pairs.

1. Understanding the Base Pairing in DNA:
In DNA, base pairing follows the rule of complementary base pairing: Guanine (G) pairs with Cytosine (C), and Adenine (A) pairs with Thymine (T). The number of hydrogen bonds between base pairs is as follows:

• G-C pairs have 3 hydrogen bonds.
• A-T pairs have 2 hydrogen bonds.

2. Analyzing the Pitch and Base Pair Relationship:
The pitch of the DNA molecule (the distance for one full turn of the helix) is 170°. Since each base pair contributes a certain number of hydrogen bonds, we need to match the number of hydrogen bonds to the options provided.

3. Determining the Correct Combination:
Given that there are 130 hydrogen bonds between the base pairs, and we know that G-C pairs contribute 3 hydrogen bonds and A-T pairs contribute 2 hydrogen bonds, we can set up the equation:

• Let the number of G-C pairs be x, and the number of A-T pairs be y.
• From the problem, we have the equation: 3x + 2y = 130.
• Additionally, the total number of base pairs should add up to the total number of base pairs, which we can estimate by testing the options.

4. Checking the Options:
After substituting the values from the given options, we find that the correct combination is:

Final Answer:
The correct answer is (D) 30, 20.