Multiple Choice
In the B-form DNA double helix, approximately how many times longer is one helical turn than the diameter (width) of the helix?
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7. DNA and Chromosome Structure
DNA Structure
Multiple Choice
In the DNA double helix, what chemical components make up the “sides” (backbone) of the molecule?
A
A continuous chain of amino acids linked by peptide bonds
B
Alternating deoxyribose sugars and phosphate groups (a sugar-phosphate backbone)
C
Alternating ribose sugars and phosphate groups (a ribose-phosphate backbone)
D
Alternating nitrogenous bases paired by hydrogen bonds
Verified step by step guidance1
Understand the structure of DNA: DNA is composed of two strands forming a double helix.
Identify the components of each strand: Each strand consists of repeating units called nucleotides.
Recognize that each nucleotide is made up of three parts: a nitrogenous base, a sugar molecule, and a phosphate group.
Focus on the 'sides' or backbone of the DNA helix: these are formed by the sugar and phosphate groups linked together.
Note that in DNA, the sugar is deoxyribose, so the backbone is an alternating chain of deoxyribose sugars and phosphate groups connected by phosphodiester bonds.
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