Question

Length of one turn of DNA is
A. 34 ${{A}^{\circ }}$
B. $3.4{{A}^{\circ }}$
C. $0.34{{A}^{\circ }}$
D. 20 ${{A}^{\circ }}$

Answer 1

The type of DNA present in the Eukaryotes is referred to as B DNA. As the most frequently occurring double-helical structure, B-DNA is found in nature. Having 10 base pairs per turn, it is right-handed in orientation.

Complete answer:
A polymer of nucleotides in DNA or deoxyribonucleic acid. A nitrogenous base that may be purine (Adenine, Guanine) or pyrimidine (Cytosine, Thymine), a group of sugar and phosphate, contains each nucleotide. Such nucleotides act as the building blocks for DNA. On the outer side of the double-stranded helix of DNA, the sugar-phosphate backbone is located while nucleotide bases are present on the inner side of the helix. Each complete turn of a double-helical DNA consists of 10 base pairs of nucleotides with 34 angstroms being the length of the complete turn. The length of eukaryotic fragments of DNA with 10 pairs of nucleotides would therefore be $34$angstroms.
The double-helical structure of DNA is where the two strands are coiled over each other tightly. B- With the dominant and minor groove, DNA has a right-handed helix. The DNA's diameter is $20A$.
In a single turn, the number of base pairs is 10 and the distance between base pairs is $3.4A$.

Thus, the cumulative DNA length of one turn is $10\text{ }x\text{ }3.4\text{ }=~34A$
So, choice A is the correct answer.

Note: The genetic material containing inherited knowledge in most species is DNA or Deoxyribonucleic acid. These are biological macromolecules that contribute to cell regulation as well as play a crucial role in protein formation. B DNA is the most commonly occurring type of double-helical DNA under normal physiological circumstances. It is a right-handed helical structure that runs in the opposite direction with double strands. Via the X-ray diffraction method, Watson and Crick found this double-helical structure of DNA.