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Question
The fact that a purine base always pairs through hydrogen bonds with a pyrimidine base in the DNA double helix leads to:
The fact that a purine base always pairs through hydrogen bonds with a pyrimidine base in the DNA double helix leads to:
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Solution
The correct option is A uniform width throughout DNA
The antiparallel nature:
Antiparallel nature of DNA means that the two DNA strands have opposite polarity, that is one strand runs in 3′→5′ direction and the other strand runs in 5′→3′.
The semiconservativ e nature:
The semiconservative nature is attributed to DNA replication. Once DNA replication completes, each DNA molecule formed has one parental strand and one newly synthesised DNA strand. This mode of replication is called semiconservative.
Uniform width throughout DNA:
The two DNA strands are joined together to form the double helix structure, due to the base pairing of nitrogenous bases in the two strands.
Adenine and guanine are purines. They have two heterocyclic rings fused together in their structure. Thymine and cytosine are pyrimidines. They have a single heterocyclic ring in their structure.
When the purines pair with pyrimidines the width remains the same as a double ringed structure binds with a single ring. Here the hydrogen bond has a fixed bond length which maintains the constant width of DNA.
Hence the purine of one strand forms a hydrogen bond with a pyrimidine of another strand.
Uniform length in all DNA:
DNA does not have uniform length in all the species.
Final answer: c. uniform width throughout DNA
The antiparallel nature:
Antiparallel nature of DNA means that the two DNA strands have opposite polarity, that is one strand runs in 3′→5′ direction and the other strand runs in 5′→3′.
The semiconservativ e nature:
The semiconservative nature is attributed to DNA replication. Once DNA replication completes, each DNA molecule formed has one parental strand and one newly synthesised DNA strand. This mode of replication is called semiconservative.
Uniform width throughout DNA:
The two DNA strands are joined together to form the double helix structure, due to the base pairing of nitrogenous bases in the two strands.
Adenine and guanine are purines. They have two heterocyclic rings fused together in their structure. Thymine and cytosine are pyrimidines. They have a single heterocyclic ring in their structure.
When the purines pair with pyrimidines the width remains the same as a double ringed structure binds with a single ring. Here the hydrogen bond has a fixed bond length which maintains the constant width of DNA.
Hence the purine of one strand forms a hydrogen bond with a pyrimidine of another strand.
Uniform length in all DNA:
DNA does not have uniform length in all the species.
Final answer: c. uniform width throughout DNA
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