Question

The right handed DNA form is
A.A and B
B.C and Z
C.Z and A
D.B and Z

Answer 1

Hint:- There are three different forms of DNA, A, B & Z, among these Z forms of DNA are left -handed. The helix of ordinary DNA is right-handed. Left-handed helices have been created experimentally and may be present in different living cells.

Complete step-by-step solution:- A-form DNA
A-DNA is a right-handed double helix composed of deoxyribonucleotides. It shows up when the humidity of the environment is under 75%, which implies that it is once in a while present in ordinary physiological condition. The two strands of A-DNA are anti parallel with one another and not symmetrical. It is asymmetrical on the grounds that the glycosidic bonds of a base pair are not oppositely inverse to one another. Accordingly, major grooves and minor grooves can be seen in each turn. One turn of the helix comprises of 11 base sets with a length of 2.86nm. The foundation of A-DNA is framed by sugar phosphates that are connected consistent utilizing phosphodiester bonds. All the nitrogenous bases are at the center focus of the helix. Hydrogen bonds between nitrogenous bases permit the molecule to show the double helix structure. The helix width of A-DNA is 2.3nm. Generally speaking, A-DNA is more extensive than the more normally discovered B-DNA.

B-form DNA

B-form DNA is a right-handed double helix, which was found by Watson and Crick dependent on the X-ray diffraction designs. It is the basic type of DNA that exists under ordinary physiological conditions. The twofold strands of B-DNA run in antiparallel ways. The structure is symmetrical with major grooves and minor grooves present then again. The molecule is deviated on the grounds that the glycosidic bonds of a base pair are not oppositely inverse to one another. In one turn, there are 10 base sets with a length of 3.4nm. The separation between contiguous deoxyribonucleotides is 0.34nm. Same as A-DNA, the foundation of B-DNA is framed by sugar phosphates that are connected nonstop utilizing phosphodiester bonds and the center area comprises nitrogenous bases. The two strands are held together by hydrogen bonds between nitrogenous bases. The helix width of B-DNA is 2nm. B-DNA is smaller than A-DNA.

Z-form DNA

Z-structure DNA is a left-handed double helix. It has an altogether different structure when contrasted and A-DNA and B-DNA. The crisscross appearance of backbone permits it to be recognized from different types of DNA. The helix width is 1.8nm, which is the tightest among the three sorts. The structure comprises major and minor grooves. One turn of Z-DNA has 12 base pairs and the length is 4.56nm. The separation between two nearby deoxyribonucleotides is 0.37nm. Same as different types of DNA, hydrogen bond is available to hold the two strands together. Z-DNA is hard to see since it is unstable. It very well may be found in microscopic organisms, eukaryotes and infections. In some infections, they require Z-DNA binding proteins for pathogenesis.
So,The correct option is A.

Note:-
The right-handed double helical Watson – Crick Model for B-structure DNA is the most regularly realized DNA structure.

Notwithstanding this exemplary structure, a few different types of DNA have been watched.

The helical structure of DNA is in this way factor and relies upon the sequence and the environment.

There is basically not sufficient space for the DNA to be loosened up in an ideal, direct B-DNA conformation. In virtually all cells, from transparent microbes through complex eukaryotes, the DNA must be compacted by in excess of 1,000 overlap all together even to fit inside the cell or nucleus.

Refined goal of the structure of DNA, in light of X-ray crystallography of short engineered bits of DNA, has indicated that there is a significant difference in the helical structure of DNA, in view of the arrangement.