Synthesis of DNA can be outlined by the following steps:
A. Joining of phosphoric acid unit to C-5 of nucleoside.
B. Complementary base pairing between the strands.
C. Joining of C-1 of pentose sugar to nitrogen of the base.
D. Formation of phosphodiester linkage between C-5 of one nucleotide and C-3 of another.
Choose the correct answers from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → C, A, D, B
DNA is built up from its units in this order:
(C) The base joins the C-1′ of the pentose sugar → a nucleoside
(A) Phosphoric acid joins the C-5′ of the sugar of the nucleoside → a nucleotide
(D) Nucleotides are linked by phosphodiester bonds between C-5′ of one and C-3′ of the next → a polynucleotide strand
(B) Two strands are held together by complementary base pairing (A with T, G with C) → the double helix
NCERT (2026-27 edition):
Structure of Nucleic Acids – “A unit formed by the attachment of a base to 1′ position of sugar is known as nucleoside. In nucleosides, the sugar carbons are numbered as 1′, 2′, 3′, etc. in order to distinguish these from the bases (Fig. 10.5a). When nucleoside is linked to phosphoric acid at 5′-position of sugar moiety, we get a nucleotide (Fig. 10.5). … Nucleotides are joined together by phosphodiester linkage between 5′ and 3′ carbon atoms of the pentose sugar.”
