1. Tardigrade
  2. Question
  3. Biology
  4. 'X' is physiologically and biologically active form of DNA. The pitch of its helix is 34 Å with a distance between two adjacent base pair of about 3.4 Å . It shows right-handed coiling. Identify 'X'.

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. 'X' is physiologically and biologically active form of DNA. The pitch of its helix is $34 \, Å$ with a distance between two adjacent base pair of about $3.4 \, Å$ . It shows right-handed coiling. Identify 'X'.

NTA AbhyasNTA Abhyas 2022

Solution:

DNA in the cell is a double-stranded helix of B-form DNA which shows right handed coiling. According to the structure determined by Watson and Crick, the polar sugar-phosphate backbones of each strand form the helical scaffold, while the nitrogenous bases are nearly perpendicular to the helical axis in the interior of the molecule. Each base forms hydrogen bonds with a base from the opposite strand. The diameter of the B-DNA is 20 Angstroms, and the distance between base pairs is $\sim 3.4$ Angstroms. The polarity of the backbones is antiparallel, with one strand running $3^{′} \rightarrow \, 5′$ and the other $5^{′} \rightarrow 3′$ direction.