Answer:
The major structural forms of DNA are A- DNA, B-DNA, and Z-DNA.
There are several differences among the 3 DNAs in their helix turn, number of nucleotides, distance between the base pairs, etc.
Step-by-step explanation:
DNA is a double-stranded helix. These are the twisted ladders where base pairs are attached by hydrogen bonds. There are 3 major forms of DNA such as A - DNA, B- DNA, and Z - DNA. They are different from each other by their helix type, diameter or complete turn, and distance between the 2 base pairs.
A - DNA: This type of DNA was discovered by Rosalind Franklin. It was discovered by the X-ray diffraction method. Its helixes are right-handed. The helixes are shorter than the B - DNA. The diameter of the helix is 2.55nm. The distance between the base pair/rise is 0.29nm. The number of base pairs per complete turn is 11.
B - DNA: This is the common type of DNA structure. This is the Watson and Crick model of DNA. The helix is right-handed and the diameter is 2.37nm. The distance of a complete turn is 3.4nm. The rise per base pair or the distance between 2 base pairs in B-DNA is 0.34nm. The number of base pairs per complete turn of the helix is 10 nucleotides.
Z -DNA: It is the left-handed DNA. This type of DNA was discovered by Robert Wells and colleagues. This DNA is in a zig-zag form. So it is called Z-DNA. It is long and thin than other DNA. The distance per turn is 4.5 nm. and rise per base pair is 0.37 nm. The number of base pairs per complete turn is 12 nucleotides. The minor groove is deep.
If the B-DNA is compressed it becomes the A-DNA and if the B-DNA is expanded it turns into a Z- DNA.