Question

"Which of the following DNA double helices would be more difficult to separate into single-stranded molecules by treatment with heat (which breaks hydrogen bonds)?

Indicate the reason (or reasons) for your choice.
A:
GTATTAGAACATCTC
CATAATCTTGTAGAG
B:
TGAGCGTTCCAGCAG
ACTCGCAAGGTCGTC
Mark the correct boxes below:

1) DNA molecule A
2) DNA molecule B
3) DNA molecule A has a lower A-T content
4) DNA molecule B has a higher G-C content
5) DNA molecule A has a higher G-C content
6) DNA molecule A has a higher A-T content

Answer 1

DNA molecule B with a higher G-C content would be more difficult to denature with heat due to more hydrogen bonds between guanine and cytosine compared to DNA molecule A which has a higher A-T content.option 2 and 4 is correct answer.

Step-by-step explanation:

Among the two DNA molecules presented, DNA molecule B would be more difficult to separate into single-stranded molecules by treatment with heat. The reason for this is primarily due to the hydrogen bonds that form between the nitrogenous bases on the interior of DNA.

It is known that guanine and cytosine (G-C) are connected by three hydrogen bonds, while adenine and thymine (A-T) are connected by two.

Comparing the two sequences, DNA molecule A has a higher A-T content which means fewer hydrogen bonds to break. Hence it would require less energy (heat) to denature. On the other hand, DNA molecule B has a higher G-C content, consequently, it has more hydrogen bonds that would need to be disrupted to separate the strands, making it more heat-resistant.

The correct choices are:

• 2) DNA molecule B
• 4) DNA molecule B has a higher G-C content