Multiple Choice
Which of the following lists correctly identifies the four nitrogenous bases found in DNA?
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7. DNA and Chromosome Structure
DNA Structure
Multiple Choice
In the DNA double helix, what type of interaction must be disrupted for the two strands to separate during processes such as replication or PCR denaturation?
A
Hydrogen bonds between complementary nitrogenous bases
B
Covalent phosphodiester bonds in the sugar-phosphate backbone
C
Peptide bonds linking nucleotides together
D
Glycosidic bonds between the base and the deoxyribose sugar
Verified step by step guidance1
Understand the structure of the DNA double helix: it consists of two strands held together by interactions between nitrogenous bases and a sugar-phosphate backbone.
Identify the types of bonds present: covalent phosphodiester bonds link nucleotides within each strand, hydrogen bonds connect complementary bases between strands, glycosidic bonds connect bases to the sugar, and peptide bonds are not involved in DNA structure.
Recognize that during strand separation (such as in replication or PCR denaturation), the backbone remains intact, so covalent phosphodiester bonds are not broken.
Focus on the bonds between the two strands: hydrogen bonds between complementary nitrogenous bases (A-T and G-C pairs) must be disrupted to separate the strands.
Conclude that breaking hydrogen bonds between complementary bases allows the two DNA strands to separate without breaking the covalent backbone.
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