In the MC section Q15, Insight 2010, how can the two fragments of a DNA strand have different melting temperatures? Initially when I first scanned the question I thought it had something to do with the size of the different bases, pyrimidines having a single ring structure and purines a double ring structure. Though when I read it properly I noticed that the question said the melting temperature is the temperature at which 50% of the strand separates into single strands. But how can one strand separate without the other complementary strand separating too? Hence shouldn't the melting temperature of both fragments of a double helix be at equal temperature.
Here is the question:
The melting temperature of a piece of double-stranded DNA is the temperature at which 50% of the strands separates into single strands. Two fragments of DNA of equal length have different melting temperatures. The melting temperature of fragment A is higher than that of fragment B. This is bes explained by
A) Fragment A has a greater percentage of adenine bases than fragment B.
B) Fragment B has a greater percentage of cytosine bases than fragment A.
c) Fragment A has a higher number of disulfide cross-links than fragment B.
d) Fragment A has a greater percentage of guanine bases than fragment B.
The answer is D.
I'm confused about the wording of the question.
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