Multiple Choice
In the context of DNA structure, what is the basic monomer unit of DNA called?
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7. DNA and Chromosome Structure
DNA Structure
Multiple Choice
Which of the following DNA molecules is expected to be the most thermodynamically stable under physiological salt conditions, assuming all are the same length and fully paired (no mismatches)?
A
A double-stranded DNA molecule containing many abasic (AP) sites
B
A double-stranded DNA molecule with the highest GC content
C
A double-stranded DNA molecule with the highest AT content
D
A single-stranded DNA molecule with the highest GC content
Verified step by step guidance1
Understand that DNA stability under physiological salt conditions depends largely on base pairing and base stacking interactions.
Recall that guanine-cytosine (GC) pairs form three hydrogen bonds, whereas adenine-thymine (AT) pairs form only two, making GC pairs more thermodynamically stable.
Recognize that abasic (AP) sites lack a base, disrupting hydrogen bonding and base stacking, which decreases stability.
Note that double-stranded DNA is generally more stable than single-stranded DNA because of complementary base pairing and stacking interactions.
Conclude that among the options, the double-stranded DNA molecule with the highest GC content will be the most thermodynamically stable due to stronger hydrogen bonding and stacking.
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