B-DNA is a helical structure with a diameter of 20A˚ and the distance between the two base pairs is 3.4A˚. There are 10 base pairs in each turn; hence, one turn of the helix (pitch of each helix) is approximately 34A˚ or 3.4 nm(10=1.0 nm). Related Theory There are three different DNA types: (i) A-DNA: It is a right-handed double helix similar to the B-DNA form. Dehydrated DNA takes an A form that protects the DNA during extreme condition such as desiccation. (ii) B-DNA: The most common DNA conformation which is a right-handed helix, normal physiological conditions. (iii) Z-DNA: Z-DNA is a left-handed DNA where the double helix winds to the left in a zig-zag pattern and play some role in gene regulation.
One turn of the helix in a B-form DNA is approximately:
NEET UG 2006 — Zoology Molecular Basis of Inheritance
2006mcqeasy
One turn of the helix in a B-form DNA is approximately:
Official previous-year question
Held on 30 Apr 2006 · Verified 9 Jul 2026.
Options
- A
2 nm
- B
20 nm
- C
0.34 nm
- D
3.4 nm
Did you get this right?
Sign in to track your attempts and accuracy.
Your note
Sign in to keep a private note on this question. Nothing you write is ever public.
NEET UG Molecular Basis of Inheritance in other years
Molecular Basis of Inheritance 2025Molecular Basis of Inheritance 2024Molecular Basis of Inheritance 2023Molecular Basis of Inheritance 2022Molecular Basis of Inheritance 2021Molecular Basis of Inheritance 2020Molecular Basis of Inheritance 2019Molecular Basis of Inheritance 2018Molecular Basis of Inheritance 2017Molecular Basis of Inheritance 2016Molecular Basis of Inheritance 2015Molecular Basis of Inheritance 2014
More NEET UG Molecular Basis of Inheritance questions
Which of the following are the post-transcriptional events in an eukaryotic cell? A. Transport of pre-mRNA to cytoplasm prior to splicing. B. Removal of introns and joining of exons. C. Addition of methyl group at 5' end of hnRNA. D. Addition of adenine residues at 3 ' end of hnRNA. E. Base pairing of two complementary RNAs. Choose the correct answer from the options given below :
2025medium
Histones are enriched with -
2025easy
Who proposed that the genetic code for amino acids should be made up of three nucleotides?
2025easy
Match List I with List II: $\begin{array}{|l|l|l|l|}\hline & \text{List - I} & & \text{List - II} \\\hline \text{A}. & \text{Alfred Hershey and Martha Chase} & \text{(i)} & \text{Streptococcus pneumoniae} \\\hline \text{B.} & \text{Euchromatin} & \text{(ii)} & \text{Densely packed and dark-stained} \\\hline \text{C.} & \text{Frederick Griffith} & \text{(iii)} & \text{Loosely packed and light-stained} \\\hline \text{D.} & \text{Heterochromatin} & \text{(iv)} & \text{DNA as genetic material confirmation} \\\hline\end{array}$ Choose the correct answer from the options given below:
2025medium
Given below are two statements : Statement I : In the RNA world, RNA is considered the first genetic material evolved to carry out essential life processes. RNA acts as a genetic material and also as a catalyst for some important biochemical reactions in living systems. Being reactive, RNA is unstable. Statement II: DNA evolved from RNA and is a more stable genetic material. Its double helical strands being complementary, resist changes by evolving repairing mechanism. In the light of the above statements, choose the most appropriate answer from the options given below :
2025medium
Other Zoology topics for NEET UG
Keep practicing Molecular Basis of Inheritance
Work through every NEET UG Molecular Basis of Inheritance PYQ, year by year.