1.
The genetic information of a cell
is stored within its DNA
(Deoxyribonucleic acid)
macromolecules.
The segment of DNA carry this
genetic information called “Genes”.

2.
 In 1869Johann Friedrich
miescher had isolated from the
pus cells obtained from the
discarded bandages.
Frederick Griffith (1928) 
demonstrated the transformation from
heat killed S-type to live R-type
streptococcus.

3.
Rosalind Franklin (1952)
 X ray diffraction image of DNA.
Watson and Crick (1953)
 concluded DNA is the
helical form.

4.
DNA is a polymer
DNA is a long polymeric molecule .
A polymer is a long chain like molecule comprising
numerous individual units called “monomers”
Nucleotides- the monomers in DNA
DNA which contains four kinds of smaller building
blocks (monomers)called deoxyribotides or
deoxyribonucleotides .

5.
The nucleotide itself a complex molecule being made
up of three components.
Nitrogenou
s base
sugar
Phosphoric
acid
Nucleotide

6.
The sugar component
The sugar component of the nucleotide is a pentose
(containing five carbon atom) called 2’-deoxyribose.
Pentose sugar can exist in two forms ,
1.straight chain (or) Fischer structure
2.ring (or) Haworth structure
The 2’-deoxyribose that occurs in nucleotide.

7.
 PURINES
1. Adenine (A)
2. Guanine (G)
A or G
 PYRIMIDINES
3. Thymine (T)
4. Cytosine (C)
T or C

8.
A pairs with T by two
hydrogen bonds
C pairs with G by three
hydrogen bonds

9.
It is a right-handed double
helix fairly similar to the more
common and well-known B-DNA
form, but with a shorter more
compact helical structure.
It contains 11 base pairs per
turn. Its is right handed but less
than the B-form DNA.

10.
It appears likely that it occurs
only in dehydrated samples of
DNA, such as those used in
crystallographic experiments, and
possibly is also assumed by
DNA-RNA hybrid helices and by
regions of double-stranded RNA.

11.
B-DNA is the form commonly
observed in chromosomes. B-DNA is a
right-handed helix with 10 base pairs
per turn.
This structure was described by
Watson and crick is the most
predominant turn of physiological
Each under the B-form
conditions. base pair spanning
has 10
a distance of 3.4nm.

12.
Z-DNA is a left handed helix generated
because of different conformation between
one of its bases and the deoxyribose sugar.
This bond is called a
The syn conformation is found in
Z-DNA .

13.
The alteration of a purine
(G) and a pyrimidine (C)
along a Z-DNA double strand
produces the anti-syn
alteration that gives the
backbone of Z-DNA a
appearance.

14.
Feature B-DNA A-DNA Z-DNA
Helix type Right handed Right handed Left handed
Helical diameter 2.37 2.55 1.84
(nm)
Distance per each
turn (nm) 3.4 3.2 4.5
Number of base
pair per turn 10 11 12
Helix axis rotation Major groove Through base pairs Minor groove
(variable)

15.
Gene expression
transcription
translation

16.
During the cell division, the
daughter cells receive an
identical copy of genetic
information from the parent
cell.
Replication is a process in
which DNA copies itself to
produce identical daughter
molecules of DNA .