The document describes the central dogma of molecular biology, focusing on DNA replication, which is a crucial process for biological inheritance. It outlines the mechanisms of semiconservative replication, including the roles of various enzymes such as DNA polymerase, helicase, and primase, as well as details on replication patterns and fidelity. Finally, it explains the steps of initiation, elongation, and termination during DNA replication.

1. Central dogma
Replication Transcription Translation
PROTEIN
Reverse
transcripti
on

2. DNA replication is a biological process that
occurs in all living organisms and copies
their exact DNA. It is the basis for biological
inheritance.
is the process of synthesis
daught er DNA from par ental DNA
by
of
the
enzyme DNA Pol merase.
PPi
( d N M P )
dNTP
- (dNMP )
DNA Lengthened DNA

3. DN
A
Replication
Parental strand
Daughter stand

4. DNA Replication •
A reaction in which daughter DNAs are
synthesized using the parental DNAs as
the template.
•
• Transferring the
the descendant
gener ation
fidelity.
Replication
to
with a high
Parental DNA
Daughter DNA

5. Three possible replication patterns:
Semiconservative replication
Conservative replication
Dispersive replication

6. After one round
of replication
Semiconservative
replication
(A)
0MK-<
(8)
Conservative
replication
VO0MK
•
Dispersive
replication

7. Each parent strand serves as a template
for a new strand and the two new DNA
st rand s each have one old
strand
and one new
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Parent strands
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8. •
•
•
•
Semi-conservative replication
Bidirectional replication
Semi-continuous replication
High fidelity

9. [1958]
demonstrated Semiconservative
replication
DNA o rtreted an d cen t ri fu g ed
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10. » Semiconservative
Replication
Half of the parental DNA molecule
is conserved in each new double helix,
paired with a newly synthesized
complementary strand. This is called
semiconservative replication.

11. Bidirectional Replication
• Replication starts from unwinding the
dsDNA at a particular point (called
), followed by the
synthesis on each
strand.
The parental dsDNA and two newly
formed dsDNA form a Y-shape
structure called
•

12. 3'
5'
"
Leading
strand
' gr 5 '
3'
Direction ofmovement
ofreplication fork
s'
O k a z a k i •
fragments_g·3'' "
""
3' Lagging
5· s t r an
d

13. Replication Enzymes & Proteins
•DNA Polymerase - Matches the correct
nucleotides then joins / polymerizes
adjacent nucleotides to each other.
• Helicase - Unwinds the DNA and melts
.
1t.
• Primase - Provides
an
start polymerization.
A primer to

14. �
Single Strand Binding Proteins -Keep the
DNA single stranded after it has been melted
by helicase
• Gyrase - A topisomerase that Relieves
torsional strain in the DNA molecule.
• Ligase - Joins adjacent DNA strands
together (fixes "n icks")
• Telomerase - Finishes off the ends of
strands in Eukaryotes
DNA

15. DNA Polymerases of Prokaryotes
DNA Pol merase-1
• The first
(DNA Pol -I ) was
discovered in 1958 by Arthur
Kornberg who received Nobel
Prize in physiology & medicine
1959.
in
• DNA Polymerase is considered
as Kornber g Enzvme.

16. •Later,
were identified.
and
• All of them possess the
biological activity.
following
1.5'-)3' Polymerse activity
2. Exonuclease activity

17. Exonuclease functions
3 »5' exonuclease
activity
excise mismatched
nuleotides
5' »3'
exonuclease
activity
removes
primer
excise
mutated
segment
or

18. DNA Polmerase - I
•Mainly
responsible for
repairing DNA
damage

19. DNA Polymerase-I I
•T emporarily functional when DNA-
pol
and DNA-pol III are not functional.
• Still capable for doing
I
• Participates in process.

20. DNA Polymerase - III
• A heter odimer enzyme composed of
ten different subunits
• Having the polymerization
activity (10 nt/min)
• The tr ue enzyme responsible for
the pr ocess

21. Structure of DNA-pol III
has 5' » 3'
0:
polymerizing activity
&: has 3' » 5
exonuclease activity and
plays a key role to ensure
the replication fidelity.
(): maintain heterodimer
structure

22. DNA Replication, like all biological
polymerization processes, proceeds in
three enzymatically catalyzed and
coordinated steps:
initiation
elongation
and
termination

23. DNA Replication
DNA replication includes:
--initiation -- replication begins at an
ori gin of replication
- elongation - new strands of DNA are
synthesized by DNA polymerase
t e r m i n a t i o n replication is terminated
differently in prokaryotes and
eukaryotes

24. Initiation

25. Cont..
The separation of the two single strands of
DNA creates
'fork'.
a'Y' shape called a replication
• • F
t a
$
as°".. -
• d d
" Rep lica t io n F o r k F o r m i n g

26. A Primase
•
•
Also called
Primase
using
the
is able to synthesize primers
as the substrate and
as the template.
are short RNA fragments of a
nucleotides long.
several

27. A Pri ase
•
•
Also called
Primase is able to synthesize primers
NTPs as the substrate and
using free
the ssDNA as the template.
are short RNA fragments of a
several nucleotides long.

28. l
primer
5 5
5 5
New DNA
DNA template
5'
5
5
5
!Ptimase
5' 3
R.N
A
O
N
A
p
o
l
y
m
t

29. DNA replication
fork
leading
strand
3'
DNAunzips
continuous
3
,
5 discontinuous
okazaki
fragment
> ' '
laggingstrand s
·

30. 3
5' 5
Newly
Synthesized
DNA Strand 3'
} a s
s'hhhlhhhhhll d h d l l l l l , Direction of
Replication
Fo rk
Movement
Okazaki Fragments
Okazali 'ragments

31. Z I Z I I S E I E E S Z I 3 I 3 L .
Chromosome
Freenucleotides
T
DNA
polymerase
l eading
strand
Helicas
e
lagging
strand
Original
(templa
te)
DNA
77!
Replicatio
n
fork
a Adenine
c Thymine
- Cytosine
- Guanine DNA
polymerase
Original(template) DNA
strand
C )
r

32. Once all of the bases are matched up (A with
T, C with G), an enzyme called exonuclease
strips away the primer(s).
The gaps where the primer(s) were are then
filled by yet more complementary
nucleotides.