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The two polynucleotide chains in DNA are
A
discontinuous
B
antiparallel
C
semiconservative
D
parallel
Detailed Solution
According to the double helix model of Watson and Crick, DNA is made of two polynucleotide chains coiled around a common axis.
The two chains are antiparallel: one is aligned in the $5' \rightarrow 3'$ direction and the other in the $3' \rightarrow 5'$ direction.
This means that the $5'$ end (phosphate) of one chain lies opposite the $3'$ end (hydroxyl) of the other.
The bases of the two chains pair through hydrogen bonds: adenine with thymine (two hydrogen bonds) and guanine with cytosine (three hydrogen bonds).
'Semiconservative' describes the mode of DNA replication and 'discontinuous' describes the synthesis of the lagging strand; neither describes the arrangement of the two chains.
So the two polynucleotide chains in DNA are antiparallel.
The two chains are antiparallel: one is aligned in the $5' \rightarrow 3'$ direction and the other in the $3' \rightarrow 5'$ direction.
This means that the $5'$ end (phosphate) of one chain lies opposite the $3'$ end (hydroxyl) of the other.
The bases of the two chains pair through hydrogen bonds: adenine with thymine (two hydrogen bonds) and guanine with cytosine (three hydrogen bonds).
'Semiconservative' describes the mode of DNA replication and 'discontinuous' describes the synthesis of the lagging strand; neither describes the arrangement of the two chains.
So the two polynucleotide chains in DNA are antiparallel.