Practicing Success

Target Exam

CUET

Subject

Biology

Chapter

Molecular Basis of Inheritance

Question:
Which among the following is not a feature of double helix model of DNA ?
Options:
Two chains have anti-parallel polarity .
The pitch of the DNA is 3.4 nm .
The two chains are coiled in a left-handed fashion .
A purine always comes opposite to a pyrimidine .
Correct Answer:
The two chains are coiled in a left-handed fashion .
Explanation:
The two chains are coiled in a right-handed fashion. The pitch of the helix is 3.4 nm.It is made of two polynucleotide chains, where the backbone is constituted by sugar-phosphate.Guanine is bonded with Cytosine with three H-bonds. As a result, always a purine comes opposite to a pyrimidine .