Multiple Choice
In DNA structure, what is the name of the “twisted ladder” shape formed by two antiparallel strands?
7. DNA and Chromosome Structure
DNA Structure
Multiple Choice
Which of the following lists correctly identifies the four nitrogenous bases found in DNA?
A
Adenine, thymine, cytosine, and uracil
B
Thymine, uracil, cytosine, and guanine
C
Adenine, thymine, cytosine, and guanine
D
Adenine, uracil, cytosine, and guanine
Verified step by step guidance1
Recall that DNA is composed of four nitrogenous bases which are categorized into two groups: purines and pyrimidines.
Identify the purines in DNA: adenine (A) and guanine (G). These have a two-ring structure.
Identify the pyrimidines in DNA: cytosine (C) and thymine (T). These have a single-ring structure.
Note that uracil (U) is a nitrogenous base found in RNA, not DNA, so it should not be included in the list of DNA bases.
Therefore, the correct list of nitrogenous bases in DNA is adenine, thymine, cytosine, and guanine.
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