Question

Identify the correct statements from those given below and choose the right option.

I. The sugar present in RNA is ribose
II. Adenine forms 3 H-bonds with thymine
III. Phosphate ester of nucleoside is nucleotide
IV. Cytosine is not present in RNA but present in DNA

• A. Only I, IV are correct
• B. Only II, III are correct
• C. Only I, III are correct
• D. Only I, III, IV are correct

Answer 1

The correct option is C Only I, III are correct

DNA and RNA are polymers of nucleotides.

Each nucleotide has a pentose sugar, nitrogenous base and a phosphate group.

The sugar found in the DNA is deoxyribose sugar which is a 5-C compound (pentose sugar).

The sugar found in the RNA is ribose sugar which is a 5-C compound (pentose sugar).

Given below is the structure of ribose sugar.


Ribose has the -OH group at 2’-C position.

Adenine, guanine and cytosine are nitrogenous bases found in both DNA and RNA.

However, uracil is found in RNA and not present in DNA. Instead, DNA has thymine in place of uracil.

A nucleoside is formed when a nitrogenous base is linked to the pentose sugar through a N-glycosidic linkage.

A phosphate makes an ester bond with a nucleoside to form a nucleotide.


Adenine forms two H-bonds with thymine and cytosine forms three H-bonds with guanine.