1.
DNA GRADE 12

2.
LOCATION OF DNA IN
A CELL
Locus: Position of gene on chromosome

3.
LOCATION OF DNA IN
A CELL
•Chromatin is a complex of DNA
and protein, and is found in the
nucleus of eukaryotic cells.
•Histones are proteins that are
responsible for the first level of
DNA packing in chromatin
•The chromatin network in the
nucleus of a cell will coil up
tightly during cell division and
form individual chromosomes.

4.
DNA : A LONG LINEAR POLYMER FOUND IN THE NUCLEUS OF A CELL
AND FORMED FROM NUCLEOTIDES AND SHAPED LIKE A DOUBLE HELIX
ASSOCIATED WITH THE TRANSMISSION OF GENETIC INFORMATION .

5.
THE STRUCTURE OF DNA
http://cronodon.com/BioTech/Cell_Nucleus.html

6.
NUCLEIC ACID : (BIOCHEMISTRY) ANY OF VARIOUS MACROMOLECULES
COMPOSED OF NUCLEOTIDE CHAINS THAT ARE VITAL
CONSTITUENTS OF ALL LIVING CELLS.
TYPE OF NUCLEIC ACID :
DNA AND RNA

7.
STRUCTURE OF A NUCLEOTIDE
A nucleotide is made
of 3 components:
• A Pentose sugar
• This is a 5 carbon
sugar
• The sugar in RNA is
ribose.
• The sugar in DNA is
deoxyribose.

8.
STRUCTURE OF A NUCLEOTIDE
• A Phosphate group
• Phosphate groups are
important because
they link the sugar on
one nucleotide onto
the phosphate of the
next nucleotide to
make a
polynucleotide.

9.
STRUCTURE OF A NUCLEOTIDE
• A Nitogenous base
• In DNA the four bases are:
• Thymine
• Adenine
• Cytosine
• Guanine
• In RNA the four bases are:
• Uracil
• Adenine
• Cytosine
• Guanine

10.
WHAT IS DNA
• A nucleic acid that contains genetic
information.
• Double helix shape
• Composed of nitrogenous bases (adenine,
cytosine, guanine and thymine), a five-carbon
sugar (deoxyribose), and a phosphate
molecule.

11.
SUGAR PHOSPHATE BONDS
(BACKBONE OF DNA)
• Nucleotides are
connected to each other
via the phosphate on one
nucleotide and the sugar
on the next nucleotide
• A Polynucleotide
Thursday, August 24, 2017

12.
NITROGENOUS BASES – TWO
TYPES
Pyramidines
Thymine - T
Cytosine - C
Uracil - U
Purines
Adenine - A
Guanine - G
Thursday, August 24, 2017

13.
ADENINE

14.
GUANINE
Thursday, August 24, 2017

15.
COMPLEMENTARY BASE PAIRING
Purines Pyramidines
Adenine Thymine
Adenine Uracil
Guanine Cytosine

16.
BASE PAIRING
• The Nitrogenous
Bases pair up with
other bases. For
example the bases of
one strand of DNA
base pair with the
bases on the
opposite strand of
the DNA. Thursday, August 24, 2017

17.
THE RULE:• Adenine always base pairs with Thymine (or Uracil if
RNA)
• Cytosine always base pairs with Guanine.
• This is beacuse there is exactly enough room for
one purine and one pyramide base between the two
polynucleotide strands of DNA.

18.
3.DISCOVERY OF
THE DNA STRUCTURE
•Early in the 20th century, the identifi-
cation of the molecules of inheritance
loomed as a major challenge to
biologists.

19.
•Discovery of the genetic role of DNA began with research by Frederick
Griffith in 1928.
•Griffith worked with 2 strains of a bacterium, 1 pathogenic (S cells) & 1
harmless (R cells)
•Heat-killed pathogenic strain were mixed with living cells of harmless
strain and the result = some living cells became pathogenic.
•This phenomenon was called transformation, now defined as a change in
genotype & phenotype due to assimilation of foreign DNA.

20.
1952: A. Hershey & M. Chase experiments
showing that DNA is the genetic material
of T2 phage.
To determine the source of genetic
material in the phage, they designed an
experiment showing that only 1 / 2
components of T2 (DNA or protein) enters
an E. coli cell during infection
They concluded that the injected DNA of
the phage provides the genetic
information

21.
4. THE ROLE OF DNA
•DNA is vital for all living beings
– even plants.
•It is important for:
•inheritance,
•coding for proteins and
•the genetic instruction guide
for life and its processes.
DNA holds the instructions for
an organism's or each cell’s
development and reproduction
and ultimately death.
DNA can replicate itself.

22.
NON-CODING DNA
Multicellular eukaryotes have many introns(non-
coding DNA) within genes and noncoding DNA
between genes.
The bulk of most eukaryotic genomes consists of
noncoding DNA sequences, often described in the
past as “junk DNA”
Much evidence indicates that noncoding DNA plays
important roles in the cell.
Sequencing of the human genome reveals that
98.5% does not code for proteins, rRNAs, or tRNAs.

23.
DNA REPLICATION
DNA replication is a biological process that occurs in
all living organisms and copies their exact DNA. It is
the basis for biological inheritance.

24.
DNA: REPLICATION
Thursday, August 24, 2017

25.
The first major step for the DNA Replication to take
place is the breaking of hydrogen bonds between
bases of the two antiparallel strands.
The unwounding of the two strands is the starting
point. The splitting happens in places of the chains
which are rich in A-T. That is because there are only
two bonds between Adenine and Thymine (there are
three hydrogen bonds between Cytosine and
Guanine).
Helicase is the enzyme that splits the two strands.
The structure that is created is known as
"Replication Fork".

26.
DNA UNWINDS…..

27.
Origins initiate
replication at
different times.
Thursday, August 24, 2017

28.
Thursday, August 24, 2017

29.
REPLICATION FORK
The replication fork is a structure that forms within
the nucleus during DNA replication. It is created by
helicases, which break the hydrogen bonds holding
the two DNA strands together. The resulting
structure has two branching "prongs", each one
made up of a single strand of DNA.
These two strands serve as the template for the
leading and lagging strands, which will be created
as DNA polymerase matches complementary
nucleotides to the templates; The templates may be
properly referred to as the leading strand template
and the lagging strand template

30.
DNA strands have a directionality, and the different
ends of a single strand are called the
"3' (three-prime) end" and the "5' (five-prime) end"
with the direction of the naming going 5 prime to the
3 prime region.
The strands of the helix are anti-parallel with one
being 5 prime to 3 then the opposite
strand 3 prime to 5.
These terms refer to the carbon atom in deoxyribose
to which the next phosphate in the chain attaches.
Directionality has consequences in DNA synthesis,
because DNA polymerase can synthesize DNA in
only one direction by adding nucleotides to the 3'
end of a DNA strand.

31.
REFERENCES
• http://www.slideshare.net/guest93618/dna-
981508?qid=56427ae3-eee5-4740-a362-
2a25b50f7354&v=qf1&b=&from_search=35. Accessed on
the 06 March 2014
• http://www.slideshare.net/lissyjyothish/dna-
9042838?qid=56427ae3-eee5-4740-a362-
2a25b50f7354&v=qf1&b=&from_search=25. accessed on
the 06 March 2014
• http://www.slideshare.net/amalaielmorsy/dna-
30211742?qid=56427ae3-eee5-4740-a362-
2a25b50f7354&v=default&b=&from_search=48. Accessed
on the 2014

32.
• http://www.slideshare.net/aquanat/dna-
12598390?qid=56427ae3-eee5-4740-a362-
2a25b50f7354&v=qf1&b=&from_search=52from_s
earch=66.Accessed on the 06 March 2014
• http://www.slideshare.net/guestd6e7b3/dna-
presentation-910904?qid=56427ae3-eee5-4740-
a362-
2a25b50f7354&v=default&b=&from_search=66.Ac
cessed on the 06 March 2014

33.
• LINK TO MY SLIDE SHARE
ACOOUNT
HTTP://WWW.SLIDESHARE.NET/201134827/
DNA-140120073506PHPAPP02-1-
31984050