Online Counseling Resource
YCMOU ELearning Drive…
School of Architecture, Science and Technology
Yashwantrao Chavan Maharashtra
Open University, Nashik – 422222, India
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OC-SBT083-CP1-04
Introduction
Programmes and Courses
 SEP – SBT083–Unit-01
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School of Science and Technology, Online Counseling Resource…
Credits

Academic Inputs by

Arun Punaji More.
M.Sc. (Microbiology)

Experience: 11 Years

[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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Learning Objectives

After studying this module, you should be able to:

Explain mutations.

Describe various types of mutations.

Explain mechanisms of various types of
mutations.
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Introduction - 1
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Mutation is defined as heritable abrupt change or
changes in the DNA sequence.
These inheritable changes in DNA sequences
arise spontaneously or can be induced in
laboratory using various chemicals or physical
agents which are called as mutagenic agents.
Mutation may or may not produce any
phenotypic change or disease in the organism.
In this presentation we will learn in detail the
various types of mutations and their mechanism.
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Mutations

0n the basis of how the mutations emerge
they are broadly classified into two broad
types.

Spontaneous mutations:


Arise in the absence of any external mutagenic
agent.
Arise due to errors in DNA replications.
Induced mutations:
Arise in the presence of known external
mutagenic agents.
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Spontaneous Mutations-1
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The spontaneous mutations arise due to
error in DNA replications; number of such
errors are corrected during the
proofreading by the DNA polymerase
enzyme; however some are not corrected
and are carried to the next generation.
Spontaneous mutations occur due to
exposure of DNA to cosmic rays and
oxygen radicals.
Cosmic rays alter the structure of DNA
bases.
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Spontaneous Mutations-2
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Whereas the oxygen radicals can convert
the Guanine into 8-hydroxyguanine
causing mutation.
Transposon elements cause spontaneous
mutations.
Transposons cause mutations by inserting
into the gene disrupting its sequence.
The spontaneous mutations can arise due
to tautomeric shift in nitrogenous bases of
DNA.
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Spontaneous Mutations-3

Tautomeric shift in nitrogenous base
causes transition type spontaneous
mutations.
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Spontaneous Mutations-4

These types of spontaneous mutations
caused due to tautomeric shift in
nitrogenous base pair are also described
as point substitution mutations.
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Induced Mutations-1
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
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Mutations are deliberately produced in
laboratories using mutagenic agents are
called as induced mutations.
Mutagenic agents are those chemical or
energy radiations that cause the
mutations.
The examples of chemical mutagenic
agents are


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Base analogues: 5-Bromouracil, 2Aminopurine.
Nitrous acid
Alkylating agents: ethyl methane sulfonate,
nitrosoguanidine.
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Induced Mutations-2
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Mutagenic agents:
Intercalating agents:
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Acridine
Ethidium bromide
Physical mutagens:

Ultraviolet radiation
Ionizing radiation such as x rays, cosmic rays,
gamma rays.
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Induced Mutations-3
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Base analogues:
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2-Aminopurine- acts as analogue of adenine
but unlike adenine pair with guanine and bring
about AT-->GC or occasionally GC-->AT base
pair substitution mutation.
5-bromouracil- acts as analogue of thymine
and unlike thymine pair with cytosine and
bring about AT-->GC or occasionally GC-->AT
base pair substitution mutation.
Chemicals:
Nitrous acid reacts with adenine and cytosine
and deaminate them causing the faulty base
pairing leading to AT-->GC and GC-->AT
change.
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School of Science and Technology, Online Counseling Resource…
Induced Mutations-4

Intercalating agents:
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
Acridine insert between two adjacent base
pair increasing the normal distance between
the two adjacent base pair which result into
the insertion or deletion at the time of DNA
replication.
Ethidium bromide with the same mechanism
that of acridine causes insertion or deletion
type of mutations.
Radiations :
Ultraviolet rays cause pyrimidine dimer
formation ; these dimers cause replication
error leading to deletion type of mutation.
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Induced Mutations-5

Radiations :
Ionizing radiations such as x rays, cosmic rays
and gamma rays cause ionization of water
and other chemicals surrounding the DNA;
ionization of water produces hydroxyl radicals
these ionized substances then cause
mutations into DNA.
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School of Science and Technology, Online Counseling Resource…
Point Mutations-1

A single base pair substitution mutation is
called as point mutation. Depending upon
the the phenotypic changes caused by
such single base pair substitution the
point mutations are classified into

Silent mutation:

Missense mutations:

e.g. UAC-->UAU
e.g. UAC-->CAC
Nonsense mutations:
e.g. UAC-->UAG
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School of Science and Technology, Online Counseling Resource…
Insertion and Deletion Mutations-1

Insertion or deletion of single base pair
causes shift in the reading frame of
nucleotide sequences of DNA leading to
expression of wrong polypeptide; these
type of mutation is called as frame-shift
mutation.
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School of Science and Technology, Online Counseling Resource…
Significances of Mutations
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Mutations leading to variations are used to
construct genetic map.
Mutations are used to trace genetic
history of organisms.
Mutations are used to study disease gene
and understand the mechanisms of
development of genetic disorder.
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What We Learn…..

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Various types of mutations
Mechanisms of various types of mutations.
Significances of mutations.
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Critical Thinking Question

Why frequency of spontaneous mutations
is lower than the frequency of induced
mutations?
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Hints for Critical Thinking Question


Proof reading by DNA polymerase
Random event in presence of very low
quantity of unknown mutagenic agent
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Study Tips

Book
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Title: Genetics
Author: Monroe W. Strickberger
Publication: prentice-Hall of India private
Limited
Book
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
Title: Principles of Genetics
Author: Tamarin
Publication: Tata Mcgrawhills
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End of the Presentation
Thank You !
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