Question

ADNA is
A. Right handed with 8 bp per turn
B. Right handed with 9 bp per turn
C. Right handed with 10 bp per turn
D. Right handed with 11 bp per turn

Answer 1

Hint: A-DNA is the ancient DNA found in ancient species. Helix observed in A-DNA is right handed. Number of base pairs per turn are 11. It is similar to the B-DNA. Z-DNA is a left handed helical DNA with 12 bp per spiral. Some viruses contain A-DNA.

Complete answer:
ADNA or Ancient DNA is isolated from the ancient specimens. Studies on ADNA help us to understand about the lives of the ancients. It also gives information about the genetic changes that result in the evolution of species. A-DNA was discovered by Rosalind franklin. DNA can be of different types: A-DNA, B-DNA, C-DNA, Z-DNA. Number of base pairs in each DNA is different. ADNA contains 11 base pairs per spiral. B-DNA contains 10 bp. C-DNA contains 9 bp. Z-DNA contains 12 bp per spiral. A- and B-DNA are right handed helices due to the overall stability of the stacking interactions. The base pairs of the A-DNA are not perpendicular to the helix axis as in B-DNA. Rotation per base pair occurs at 32.7⁰. Number of mean base pairs is 11. Anti glycosyl angle is present in A-DNA. The distance between nucleotide phosphate to phosphate distances is 5.9 Ȧ. The diameter of the DNA is 2.3 nm. From the above information we know that A-DNA is right handed with 11 bp per turn.

Therefore, the correct answer is option D.

Note: Z-DNA is a left handed helix. Length A-DNA is shorter than B-DNA. The major groove in A-DNA is deep and narrow, while the minor groove is wide and shallow. A-DNA is more compressed at the axis than BDNA. A-DNA is found as adaptations of hyperthermophilic archaeal viruses to survive harsh environmental conditions. Viruses such as Rudivirus, Lipotrim Viruses and Tristromavirus are some
example of viruses that have A-DNA type.