This document discusses the structure and types of DNA. It begins by introducing DNA and its components. DNA is made up of deoxyribonucleotides and carries genetic information found in chromosomes, chloroplasts, mitochondria and nuclei. The structure of DNA is a double helix formed from nucleotides containing a sugar, phosphate group and one of four nitrogenous bases. There are three main types of DNA structures: A-DNA, B-DNA, and Z-DNA. B-DNA is the most common form found in cells under normal physiological conditions. It is a right-handed double helix with 10.5 base pairs per turn and a diameter of 20 angstroms. A-DNA and Z-DNA are less common structures

1. Structure
of DNA &
Their
Types

2. Introduction
• DNA – DEOXYRIBO NUCIEIC ACID
• In 1953, Francis crick and James Watson
first described the molecular structure of
DNA .
• Found in Chromosomes, Chloroplast ,
Mitochondria and Nucleus .
• Carries the genetic information .

3. STRUCTURE
• DNA is a polymer of Deoxyribo Nucleotides
Nucleotides – 1. Sugar
2. Base
3. Phosphate group .

5. DNADoubleHelixStructure

6. DIFFERENT TYPES OF DNA
A-DNA B-DNA Z-DNA
A-DNA is a rare type of
structural conformation that a
DNA can adopt under
dehydrating conditions from B-
DNA.
A-DNA is a double stranded
helical structure almost similar
to B-DNA but with a shorter and
more compact structural
organization.
A-DNA is also a right handed
helix. The helix diameter of A-
DNA is 26 Å. and the helix pitch
(height of a turn) of A-DNA is
28.6 Å. The A-DNA contains
11.6 base pairs per turn. And the
distance between the adjacent
base pairs is 2.9 Å
The B-DNA is the most common
and predominate type of
structural conformation of DNA
in the cells. The DNA prefers to
occur in B form under the
natural physiological conditions
in the cell.
The B-DNA is better described
as the Watson- Crick Model.
Majority of the DNA in a cell is in
B-DNA conformation. B-DNA is
a right handed helix. The
distance between adjacent base
pairs in B-DNA is 3.4 Å.
The Z-DNA is a left handed
helical structure.
The double helix winds in a zig-
zag pattern. The helical
diameter of Z-DNA is 18 Å.The
total height of a helix turn is 44
Å.Each helical turn of Z-DNA
contains 12 nucleotides and The
distance between each
nucleotide is 7.4 Å.
Generally found in Plasmid of E-
Coli.

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