Which pair of sugar and base is found in RNA but not in DNA?
A
β-D-ribose and uracil
B
β-D-2-deoxyribose and uracil
C
β-D-ribose and thymine
D
β-D-2-deoxyribose and thymine
Show the answer
The answer is A.
The sugar in RNA is β-D-ribose while DNA has β-D-2-deoxyribose. RNA contains uracil in place of the thymine of DNA.
B.
2-Deoxyribose is the sugar of DNA, not RNA.
C.
Thymine occurs in DNA; RNA has uracil instead.
D.
Both 2-deoxyribose and thymine belong to DNA.
NCERT: Class 12 Chemistry, Chapter 10, 10.5
Sample 2NEET level
Consider the following statements: I. The sugar in DNA is β-D-2-deoxyribose, while the sugar in RNA is β-D-ribose. II. Thymine is present in RNA and uracil is present in DNA. III. In the DNA double helix, adenine pairs with thymine and guanine pairs with cytosine. IV. Nucleotides are joined together by phosphodiester linkages between the 5′ and 3′ carbon atoms of the pentose sugar. Which of the statements are correct?
A
I and II only
B
II and III only
C
I, III and IV only
D
II, III and IV only
Show the answer
The answer is C.
DNA contains β-D-2-deoxyribose and RNA contains β-D-ribose, and nucleotides are linked by phosphodiester bonds between the 5′ and 3′ carbons. Thymine occurs in DNA and uracil in RNA, so II is false; in the double helix A pairs with T and G with C.
A.
Statement II is false: the bases are the other way round.
B.
Statement II is false, and I and IV are also correct.
D.
Statement II is false: thymine is in DNA and uracil in RNA.
NCERT: Class 12 Chemistry, Unit 10 (Biomolecules), Nucleic Acids: Chemical Composition and Structure of Nucleic Acids
Practise Nucleic acids
Practice at the level you choose, with the answer after every question; timed tests with the answers when you submit. Every question is verified against NCERT first.