Topic: DNA
Submitted by:
Rohab Saleem. 2062
Rimsha maqsood. 2061
Ariba Saleem. 2130
Aqsa asghar . 2063
Zosha Ali waseem. 2125
Submitted to: Sir Abdurehman sb.
Class: M.Sc Botany
Institute: Khawaja Fareed college R.Y.K
Introduction: nucleic acid are the organic material
present in all organisms in the form of DNA or RNA. The
nucleic acid are formed by the combination of
nitrogenous bases, sugar molecules and the phosphate
groups. That are linked by different bonds in a series of
sequence.
Define: it is a group of molecules that is
responsible for caring and transmitting the heredity
materials from parents to off Springs.
Example: The human immuno deficiency virus
HIV contains RNA which is then converted into DNA
after attacking itself to the host cell.
Discovery: DNA was first recognised identified
by the Swiss biologist ,Johnson friedrick Miescher in
1869 during his research on white blood cells. The
double helix structure of a DND molecule was later
discovered through the experiment data by James
Watson and Francis Crick in 1953 finally, it was proved that is
possible for storing the genetic information in living organisms.
Chargaff Rule: Arvind sargaon abio chemist
discovered that the number of nitrogenous basis in
the DNA was present in equal quantities the
amount of Adenine (A) is equal to Thyamine (T) ,
where as the amount of cytosine (C) is equal to
Guanine (G).
A=T , C=G
In other words the DNA of any cell from any
organism should have a one ratio 1 of purine and
pyramidine bases.
Structure: DNA deoxyribonucleic acid
molecules are nucleic acids which are the
information caring molecules of the cell DNA
molecules are polymers and are made up of many
smaller molecules called nucleotides.
Nucleotides: It is nucleotide contain a
phosphate group, A pentose sugar and nitrogenous
base.
Pentose sugar: pantose is a monosaccharide
with 5 carbon atoms there are two types pentose
sugar is present.
Ribose sugar: ribose is a simple sugar and
carbohydrate with molecular formula C5H10O4.
Deoxyribose sugar:
It is the five sugar carbon molecule that helps form the back bone
of DNA molecules.Its molecular formula is C5H10O4.
Phosphoric acid: phosphoric acid is an
inorganic compound with the chemical formula
H3PO4.
Nitrogenous bases: A molecule that contains
nitrogen and has the chemical properties of a base the
nitrogenous bases in DNA are adenine, Guanine , Cytosine
and Thyamine.
Adenine Cytosine
Thymine Guanine
Sugar + Base = Nucleoside + Phosphate group =
Nucleotide
Salient features of Watson crick model of
DNA: 1_ The DNA is a right handed double helix it consists of two
poly deoxyribonucleotide chain twisted around each other on a
common axis.
2_ The two friends are anti parallel one stand runs in the 5 to 3
direction while the other in 3 to 5 direction.
3_ The width of a double helix is 20 A °.
4_ Each turn of The Helix is 34 A° with 10 pairs of nucleotides each fear
placed at a distance of about 3.4 A°.
5_ The two polynucleotide chains are not identical but complementary
to each other due to base pairing.
6_ The two Straits are held Together by hydrogen bonds formed by
complementary base pair the A__T pair has a two hydrogen bond while
G__C. pair has three hydrogen bones.
7_ The double helix has major grows and minor grows along the
phosphor die Easter backbone.
Major and Minor grooves:
❖ The larger groove is called major groove occurs when the back
bones are for apart while the smaller one is called the minor
groove occurs when they are closed together.
❖ Most sequence is specific DNA bindly proteins regulatory proteins
by specifically to DNA via the major groove.
❖ Groove bindly drugs almost all bind in the minor groove and are
usually somewhat A _T specific.
❖ Many non sequence specific and some sequence specific DNA
blindly proteins bind the Miner groove and often unwind and
bond DNA.
Types: There are two types of DNA these are given below;
➢ On the basis of structure
➢ On the basis of location
On the basis of structure:
• A_DNA: It was discovered by Rosahid Franklin. It is a right
hand double helix similar to the B_DNA. Dehydrated DNA takes an
a form that protect the DNA during extreme condition such as
desiccation .protein binding also remove the solvent from DNA
and DNA takes an originally identified by X-rays diffraction of
analysis of DNA fibers at 75% relative humidity at the sodium ion
potassium ions ,caesium ions present.
• B _ DNA: This is the most common DNA configuration
and it is right handed double helix this was discovered by Watson
and crick model. majority of DNA has B_ type confirmation under
normal physiological condition .most common originally reduced
from x rays diffraction of sodium salt of DNA fibres at 92% relative
humidity at the low concentration of ions.
• C_ DNA: It is formed at 66% relative humidity and in the
presence of Lithium and magnesium ions it has 7 base pairs occur.
• D_ DNA: Rare varient date base pairs per helical
turn, form in structure devoide of guanine.
• Z_ DNA: It is the left handed double helix
structure wide to the left in a zigzag pattern it was
discovered by Andres Wang and Alexander Rich. It is
found a head of the start side of a gene and hands is
believed to play some role in gene regulation.
On the basis of location:
• Nuclear DNA: It is located with the nucleus
of Eukaryotic cell it usually has two copies per
cell.The structure of nuclear DNA chromosomes is
linear with open ends and includes 46 chromosomes
containing 3 billion nucleotides.
Nuclear DNA is diploid. The mutation rate of nuclear
DNA is less then 0.3%.
• Mitochondrial DNA: It is located in the
mitochondria. It contains 100 to 1000 copies per
cell.Mitochondrial DNA chromosomes really have
closed circular structure.
Example:
16, 569 nucleotides in human.
Mitochondrial DNA is haploid coming only from the
mother .the mutation rate for mitochondrial DNA is
generally higher than nuclear DNA.
Properties of DNA:
➢ DNA helix can be right handed or left handed . but
The B_ confirmation of DNA having right handed
helix is the stable.
➢ On heating the two strands of DNA separates from
each other and on coding these again hybridize.
➢ Temperature at which strand separate completely is
known as melting temperature .melting temperature
is specific for each specific sequence.
➢ The B_Sample of DNA having higher melting point
must have more C_G content because C_G pair has
three hydrogen bones.
➢ Information in DNA is stored as a code made up of 4
chemical bases/ nucleotides bases. Adenine (A),
Guanine (G), Cytosine (C) , and. Thymine (T).
➢ Human DNA consists of about 3 billion bases and
more than 99% of those bases are the same in all
people.
➢ The bases DNA absorb ultraviolet light at wavelength
of 260 NM. the more DNA present the higher
absorption.
