DNA is the genetic material of cells that is made up of repeating nucleotides. In 1953, Watson and Crick described DNA as having a double helix structure based on an X-ray photo taken by Franklin in 1952. DNA replication allows genes, which code for specific traits, to be copied and passed on to new cells. DNA exists in three main forms - A-DNA, B-DNA, and Z-DNA - which differ in their structure including number of base pairs per turn and shape of the grooves.

1. DNA
“THE BLUEPRINT OF LIFE”
SUJITA MISHRA
PI/289 1

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Contents
History of DNA
Genetic material of cells
DNA double helix
DNA replication
ABZs of DNA 2

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DNA
(Deoxyribonucleic Acid)
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A History Of DNA
 R.FRANKLIN X-ray photo of DNA.
 (1952)
 Watson & CrickDescribed the DNA from Franklin’s x-
ray.
 (1953)
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 GENESUnits of genetic material that codes for a
specific trait.
 DNA is made up of repeating molecules called as
Nucleotides.
Genetic Material Of Cells
What IS A NUCLEOTIDE ?
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DNA Nucleotide
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DNA Double Helix
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Nitrogenous Base
PURINES
• Adenine(A)
• Guanine(G)
PYRIMIDINES
• Thymine(T)
• Cytosine(C)
A or G
T or C
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DNA Replication
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THE ABZs OF DNA
Major forms Of DNA
A-DNA  Right handed,short & broad,11bp per turn.
B-DNA Right handed,longer,thinner,10 bp per turn.
Z-DNA Left handed,longest,thinnest,12 bp per turn.
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THE ABZs OF DNA
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 Observed in active site of DNA polymerase
 Gram+ bacteria undergoing sporulation.
 Deep major groove & shallow minor groove.
 Observed under dehydrating conditions.
 B-DNAA-DNA (Reversible).
A-DNA
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 Most common DNA.
 Each base pair has same width.
 Minor groove is narrow & major groove is wide.
B-DNA
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 Seen in conditions of high salt concentration.
 Deep minor groove.
 No discernible major groove.
Z-DNA
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