Question

The total number of hydrogen bonds of a DNA-double Helix strand whose one strand has the following sequence of bases is _______ . $5^{\prime}-\mathrm{G}-\mathrm{G}-\mathrm{C}-\mathrm{A}-\mathrm{A}-\mathrm{A}-\mathrm{T}-\mathrm{C}-\mathrm{G}-\mathrm{G}-\mathrm{C}-\mathrm{T}-\mathrm{A}-3^{\prime}$

Hint:

Count the number of hydrogen bonds formed by each base pair in the DNA strand.

Answer 1

Correct Answer: 33

To determine the total number of hydrogen bonds in a DNA-double helix strand based on the given sequence, we must consider how base pairing occurs. In DNA, the bases Guanine (G) and Cytosine (C) pair together with 3 hydrogen bonds, while Adenine (A) and Thymine (T) pair with 2 hydrogen bonds. 
The provided sequence is:
5′-G-G-C-A-A-A-T-C-G-G-C-T-A-3′
Let's count the hydrogen bonds for each base pair:

• G-G: 2 Guanine bases paired with Cytosine = 2 × 3 = 6 bonds
• C: 1 Cytosine base paired with Guanine = 3 bonds
• A-A-A: 3 Adenine bases paired with Thymine = 3 × 2 = 6 bonds
• T: 1 Thymine base paired with Adenine = 2 bonds
• C: 1 Cytosine base paired with Guanine = 3 bonds
• G-G: 2 Guanine bases paired with Cytosine = 2 × 3 = 6 bonds
• C: 1 Cytosine base paired with Guanine = 3 bonds
• T: 1 Thymine base paired with Adenine = 2 bonds
• A: 1 Adenine base paired with Thymine = 2 bonds

Adding all these together gives the total number of hydrogen bonds: 6 + 3 + 6 + 2 + 3 + 6 + 3 + 2 + 2 = 33.
Thus, the total number of hydrogen bonds is 33, which falls within the specified range (33,33).

Answer 2

To determine the total number of hydrogen bonds in a DNA double-helix strand, we need to understand the base pairing rules of DNA:

• Adenine (A) pairs with Thymine (T) via 2 hydrogen bonds.
• Cytosine (C) pairs with Guanine (G) via 3 hydrogen bonds.

Given the DNA sequence:
5'-G-G-C-A-A-A-T-C-G-G-C-T-A-3'

Let's pair each base with its complementary base on the opposite strand and count the hydrogen bonds:

Base Pair	Hydrogen Bonds
G - C	3
G - C	3
C - G	3
A - T	2
A - T	2
A - T	2
T - A	2
C - G	3
G - C	3
G - C	3
C - G	3
T - A	2
A - T	2

Now, sum the total number of hydrogen bonds:

Total hydrogen bonds = 3 + 3 + 3 + 2 + 2 + 2 + 2 + 3 + 3 + 3 + 3 + 2 + 2 = 33

The total number of hydrogen bonds is 33, which is within the expected range of 33 to 33.