Download Online Counseling Resource YCMOU ELearning Drive…

Online Counseling Resource
YCMOU ELearning Drive…
School of Architecture, Science and Technology
Yashwantrao Chavan Maharashtra
Open University, Nashik – 422222, India
OC-SBT053-CP1-01
Introduction
Programmes and Courses
 SEP – SBT053 – Unit 01
School of Science and Technology, Online Counseling Resource…
Credits

Academic Inputs by

Mrs. Rasika Bhore

M.sc (Microbiology)

[email protected]
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School of Science and Technology, Online Counseling Resource…
How to Use This Resource

Counselor at each study center should use this presentation to deliver
lecture of 40-60 minutes during Face-To-Face counseling.

Discussion about students difficulties or tutorial with assignments should
follow the lecture for about 40-60 minutes.

Handouts (with 6 slides on each A4 size page) of this presentation should
be provided to each student.

Each student should discuss on the discussion forum all the terms which
could not be understood. This will improve his writing skills and enhance
knowledge level about topics, which shall be immensely useful for end
exam.

Appear several times, for all the Self-Tests, available for this course.

Student can use handouts for last minutes preparation just before end
exam.
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School of Science and Technology, Online Counseling Resource…
Learning Objectives
 After studying this module, you should be able to:
 Discuss about the different types of an enzyme
DNA Polymerase.
 Describe the functions of DNA Polymerase.
 Define ‘Primer’.
© 2007, YCMOU. All Rights Reserved.
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School of Science and Technology, Online Counseling Resource…
Introduction
 The search for an enzyme that could synthesize
DNA began in 1955.
 Work by Arthur Kornberg & colleagues led to
the purification & characterization of DNA
polymerase from E.coli cells.
 That first enzyme was DNA polymerase I, which
is a single polypeptide.
 Later investigators found that E.coli contains
atleast four other distinct DNA polymerases.
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DNA Polymerase………
 DNA polymerase helps in replication of DNA.
 It initiates replication by binding to a piece of
single-stranded DNA.
 It reads the template strand & form a
complementary strand, which is identical to the
partner of template strand.
 The elongation of chain is carried out by adding
deoxyribonucleotides to DNA.
School of Science and Technology, Online Counseling Resource…
Prokaryotic DNA Polymerase
 Bacteria (E.coli) have 5 known DNA polymerases:
 Pol I: implicated in DNA repair; has both 5'->3'(Nick
translation) and 3'->5' (Proofreading) exonuclease
activity.
 Pol II: involved in replication of damaged DNA; has 3'->5'
exonuclease activity.
 Pol III: the principal replication enzyme. It has 3'->5'
exonuclease proofreading ability.
 Pol IV: a Y-family DNA polymerase.
 Pol V: a Y-family DNA polymerase; participates in
bypassing DNA damage.
School of Science and Technology, Online Counseling Resource…
Eukaryotic DNA Polymerase

Eukaryotes have at least 15 DNA Polymerases:
 Pol α : acts as a primase (synthesizing a RNA primer), and
then as a DNA Pol elongating that primer with DNA
nucleotides.
 Pol β: implicated in repairing DNA.
 Pol γ: replicates mitochondrial DNA.
 Pol δ: main polymerase on the lagging strand, it is highly
processive and has 3'->5' exonuclease activity.
 Pol ε: primary leading strand DNA polymerase, and also
highly processive and has 3'->5' exonuclease activity.
 η, ι, κ, and Rev1 are Y-family DNA polymerases and Pol ζ is
a B-family DNA polymerase are involved in the bypass of
DNA damage.
 There are also other eukaryotic polymerases known, which
are not as well characterized: θ, λ, φ, σ, and μ.
 Only the polymerases that deal with the elongation (γ, δ and
ε) have proofreading ability (3'->5' exonuclease).
School of Science and Technology, Online Counseling Resource…
Structure Of DNA Polymerase
 DNA polymerases
have highly
conserved structure,
which means that
their overall
catalytic subunits
vary from species to
species.
 Conserved
structures usually
indicate important,
irreplicable
functions of the cell,
the maintenance of
which provides
evolutionary
advantages.
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Function Of DNA Polymerase
 DNA polymerase plays a vital role in
polymerization.
 Investigation on DNA polymerase I, have
put forward the two central
requirements of DNA polymerization:
1. DNA polymerase require a ‘Template’.
2. DNA polymerase require a ‘Primer’.
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‘Template’ For Polymerization
 Polymerization reaction of DNA
polymerase is guided by a
‘template’ DNA strand.
 According to the base-pairing
rules predicted by Watson &
Crick, where the guanine is
present in template, a cytosine
deoxynucleotide is added to the
new strand & so on.
 This discovery is important as it
provided a chemical basis for
accurate semiconservative DNA
replication.
 It also represented the first
example of the use of a template
to guide a biosynthetic reaction.
School of Science and Technology, Online Counseling Resource…
‘Primer’
Primer is a strand segment (complementary
to the template) with free 3’-hydroxyl
group to which a nucleotide can be
added.
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‘Primer’ For Polymerization
 DNA polymerase can add free nucleotides to
only the 3’ end of the newly-forming strand.
 This results in elongation of the new strand in a
5'-3' direction.
 Part of the new strand (primer) must already
be in place, DNA polymerase can only add a
nucleotide onto a preexisting strand.
 Primers consist of RNA and DNA bases with the
first two bases always being RNA, and are
synthesized by enzyme called primase.
School of Science and Technology, Online Counseling Resource…
Application of DNA Polymerase In Research
 DNA polymerase I obtained from E. coli is
used extensively for molecular biology
research.
 It’s 5' -> 3' exonuclease activity can be
simply removed from the holoenzyme to
leave a useful molecule called the Klenow
fragment.
 Klenow fragment of DNA polymerase I
has only 3’ -> 5‘ exonuclease activity, it
is widely used in molecular biology.
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What We Learn………….
 DNA Polymerase is an enzyme mainly participates in DNA
replication.
 Eukaryotes contain 15 types of DNA polymerases while
prokaryotes contain 5 types.
 DNA polymerase is made up of different sub-units having very
complex structure.
 only γ, δ and ε have proofreading ability i.e. 3'->5'
exonuclease activity.
 For the polymerization carried out by DNA polymerase,
template & primer is required.
 Klenow fragment have research value.
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Critical Thinking Questions
 What is mean by proofreading activity? If
it is absent in DNA polymerase then what
will be the consequences?
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School of Science and Technology, Online Counseling Resource…
Tips For Critical Thinking Questions
 Checking & removal of wrong bases
added in replication. It may leads in
mutation.
© 2007, YCMOU. All Rights Reserved.
School of Science and Technology, Online Counseling Resource…
Study Tips
 Book

Title: Lehninger ‘Principles
Of Biochemistry’

Author: David Nelson
• www.en.wikipedia.org
DNA polymerase
Michael Cox
 Book

Title: Genetics

Author: Peter J. Russell
© 2007, YCMOU. All Rights Reserved.
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End of the Presentation
Thank You