Multiple Choice
In nucleic acids, which nitrogenous base is found only in DNA (and not in RNA)?
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7. DNA and Chromosome Structure
DNA Structure
Multiple Choice
Which of the following statements is NOT true of DNA in most cells?
A
DNA strands have directionality with and ends.
B
DNA contains the bases adenine, thymine, guanine, and cytosine.
C
DNA uses uracil (U) instead of thymine (T) as a standard base.
D
DNA is typically double-stranded and forms a helix.
Verified step by step guidance1
Step 1: Understand the structure and composition of DNA in most cells. DNA is a nucleic acid composed of nucleotides, each containing a sugar, a phosphate group, and a nitrogenous base.
Step 2: Recall that DNA strands have directionality, meaning each strand has a 5\' end and a 3\' end, which is important for replication and transcription processes.
Step 3: Remember the four standard bases in DNA: adenine (A), thymine (T), guanine (G), and cytosine (C). These bases pair specifically (A with T, G with C) to form the double helix structure.
Step 4: Note that DNA is typically double-stranded and forms a helical structure, which is fundamental to its stability and function.
Step 5: Identify the incorrect statement by recognizing that uracil (U) is not a base found in DNA but in RNA, where it replaces thymine. Therefore, the statement claiming DNA uses uracil instead of thymine is NOT true for DNA in most cells.
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