High School Biology : Understanding Nucleotides

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #401 : High School Biology

Which of the following nucleotides is found in RNA but not DNA?

Possible Answers:

Cytosine

Adenine

Uracil

Guanine

Thymine

Correct answer:

Uracil

Explanation:

RNA and DNA both have the bases cytosine, guanine and adenine in common. In RNA, uracil is present in place of thymine which is found in DNA. 

Example Question #61 : Dna, Rna, And Proteins

Which of the following are correct base pair combinations for the DNA structure?

Possible Answers:

Cytosol paired with Guanine

Guanine paired with Thymine

Cytosine paired with Adenosine

Adenine paired with Uracil

Adenine paired with Thymine

Correct answer:

Adenine paired with Thymine

Explanation:

There are two types of nucleotides in DNA, pyrimidines and purines. The purines are Adenine and Guanine. Pyrimidines are Thymine and Cytosine. In RNA, Thymine is replaced with Uracil. Purines pair with pyrimidines in a specific order, therefore Adenine pairs with Thymine, and Cytosine pairs with Guanine. Adenine pairs with Uracil only in RNA, not DNA.

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