Question

Two double-stranded fragments of DNA are exactly the same length. At 89°C, fragment A has completely denatured, which means that the two strands have separated. At that temperature, fragment B is still double-stranded. How might these fragments differ to result in different denaturation temperatures?

Answer 1

Answer:

Fragment A have low GC bonds as compared to fragment B which means there will be low number of hydrogen bonds in the double stranded fragment A as compared to fragment B.

Explanation:

Denaturation temperature depend on the presence of hydrogen bonds in the DNA strand. There are hydrogen bonds between the complementary nucleotide in the DNA. Adenine form two hydrogen bonds thymine in the complementary strand while guanine form 3 hydrogen bonds with cytosine in the complementary strand.

The reason behind denaturation at 89°C is the presence of low number of G-C hydrogen bonds so the fragment of DNA with low number of G-C bonds in the complementary strand will denature at 89 °C as compared to other fragment B which will denature at 95 °C.