GENE MUTATION | DOES IT AFFECT A POPULATION? | WHY IT IS HAPPENING? What is a gene mutation

2. Presented by group members :-
AABIYEH
RUPAL
PINKY
PRITI
PREETI

3. MADE BY
CONTENTS
 MACROMUTATION
 MICROMUTATION
PINKY GUPTA
 INTRODUCTION GENE MUTATION
 TYPES OF MUTATION

5.  Mutations occurs at a frequency of about 1 in
 every 1 billion base pairs.
 Everybody has about 6 mutation in each cell
in
 their body .
How common are mutations
?

6. we have that many mutations ,
why don`t we look weird?

7. Mutations are not always seen . The affected gene may still function .
Mutations may be harmful
Mutations may be beneficial .
Mutations may have no effect on the organism.

8.  Mutations are a major source of genetic
variation in a population increasing
biodiversity.
 Some variations may help them to survive
better.
How do mutations affect a population ?

9. Only mutations in gametes (egg and sperm )
are passed onto offspring .
Mutations in body cells only affect the organism
in which they occur and are not passed onto
offspring.
How are mutations
inherited ?

11. MICROMUTATIONS
Change can be positive , negative , or neutral .
Can be passed to offspring if in gametes .
One or several bases
Small changes to DNA
Mutation with invisible phenotypic changes.

12. MACROMUTATION
Oligogenic in nature.
Can be easily selected in M2 generation.
It can be easily recognizable in plants.
Produce a large phenotypic effect .
Mutation with invisible phenotypic changes.

13. NUMERICAL MUTATION

14. Euploldy is the presence of chromosome
number which is the multiple of the basic
chromosome set.
EUPLOIDY

15. Types of Euploidy:
Monoploidy :- Monoploid individuals have single
basic set of chromosome, e.g., in barley 2n = x = 7
(haploid of a diploid species).
Haploid :- Haploids are individuals with
chromosome number half of the somatic number, e.g.,
in wheat (2n = 3x = 21).

16. Aneuploidy
Aneuploidy can be either due to loss of one or more chromosomes
(hypo-ploidy) or due to addition of one or more chromosomes to
complete chromosome complement (hyper-ploidy).
Aneuploidy is the presence of chromosome number that is different
fromthe simple multiple of the basic chromosome number.

17. Monosomy
Monosomy is the phenomenon where an individual lacks one or a few
non-homologous chromosome(s) of a diploid complement.
Possible monosomies in an organism
Double monosomies
(2n – 1 – 1)
Triple monosomies
(2n – 1 – 1 – 1)

18. Nullisomy (2n – 2).
Due to loss of one
pair of
chromosomes
DIPLOID
2N=6
NULLISOMY
2N - 2= 4

19. Trisomy (2n +1).
Involve addition of
either a single
chromosome
DIPLOID
2N=6
TRISOMY
2N +1= 7

20. TYPES OF GENE
MUTATION
POINT
MUTATION
OCCURS WHEN THE BASE SEQUENCES OF A
CODON IS CHANGED.
There are 3 types of gene mutations :-
Substitution
Deletion
Insertion

21. Original mutation
Point mutation
What has happened to the DNA ?

22. SUBSTITUTION MUTATION
When one nucleotide base is replaced by another.
EXAMPLE
THE FAT CAT ATE THE RAT
THE FAT HAT ATE THE RAT

23. Cont..
Normal DNA : CGA – TGC – ATC
Alanine – Threonine – Stop
Mutated DNA : CGA - TGC - TTC
Alanine - Threonine - Lysine
It may or may not affect
the amino acid or
protein. New gene still
makes sense.

24. TYPES OF
SUBSTITUTI
ON METHOD

26. TRANSITION
METHOD
A PYRIMIDINE FOR A PYRIMIDINE (C for T OR T for C)
A PURINE FOR A PURINE (A for G OR G for A )
TRANSVERSION
METHOD
A PYRIMIDINE BY A PURINE ( T by A OR G by C )
A PURINE FOR A PRIMIDINE ( A by T OR G by C )

28. :-

29. Chromosomal
Aberrations
A chromosome abnormality, disorder, abnormality,
aberration, or mutation is a missing, extra, or irregular
portion of chromosomal DNA. It can be from an atypical
number of chromosomes or a structural abnormality in
one or more chromosomes.

30. Chromosomal aberrations are of 4 major types:
DUPLICATION
INVERSION
DELETION
TRANSLOCATION

32. Part of a chromosome in
duplicate, a particular kind of
mutation (change) involving
the production of one or
more copies of any piece of
DNA, including a gene or even
an entire chromosome.
DUPLICATION

33. DELETION :- A base is removed from the DNA
sequence.

34. INVERSION
An inversion is a chromosome
rearrangement in which a segment
of a chromosome is reversed end
to end.
PERICENTRIC
INVERSION
PERICENTRIC
INVERSION

35. PERICENTRIC
INVERSION
The centromere is
the part of
inversion .

36. The centromere is
not involved.
PARACENTRIC
INVERSION

37. A chromosome translocation is a chromosome abnormality caused by
rearrangement of parts between non homologous chromosomes.
TRANSLOCATION

38. POINT MUTATION VERSUS FRAMESHIFT MUTATION

39. Silent mutation
The mutation changes one codon for
an amino acid into another codon for that
same amino acid.
It has no effect on gene’s function. Mutation goes unnoticed.

40. Why Is this possible ?
Because the
genetic code is so
repetitive .

41. it is also a change in one DNA base pair. Instead of substituting
one amino acid for another, however, the altered DNA sequence
prematurely signals the cell to stop building a protein. This type
of mutation results in a shortened protein that may function
improperly or not at all.
Non - Sense Mutation

42. Nonsense mutation

43. Missense
Mutation
This type of mutation is a change in one DNA base pair that
results in the substitution of one amino acid for another in
the protein made by a gene.

44. Missense Mutation

45. Somatic mutations occur in any of the cells of the body
except the germ cells ( sperm and egg ) and therefore
are not passed on to children .
SOMATIC MUTATION

46. It cannot be
inherited .

47. When a mutation occurs within germ cells,
it is called a germline mutation.
GERMINAL MUTATION

48. It can be
inherited .

49. Induced mutation
Those that arise after
purposeful treatment
with mutagens, environmental
agents that are known to increase
the rate of mutations.

50. Spontaneous
mutation
Spontaneous mutations are those
that arise in the absence of
known mutagen treatment.

51. CONTENTS
PHYSICAL
CHEMICAL
BIOLOGICAL
MUTAGENS
Made by
PREETI MEEL

52. MUTAGENS
Chemical and physical

54. MUTAGENS
BIOLOGICALCHEMICALPHYSICAL
RADIATION
HEAT
INTERCALATING AGENTS
BASE ANALOGE
ALKYLATING AGENTS
DEAMINATING AGENTS
METALS
TRANSPOSONS
VIRUS
BACTERIA

55. Physical mutagens
(nonionizing
radiation)
(ionizing
radiation)

56. Radiation is the process by which energy is emitted as either particles or waves. Broadly,
it can take the form of sound, heat, or light. However, most people generally use it to
refer to radiation from electromagnetic waves, ranging from radio waves, though the
visible light spectrum, and up through to gamma waves.
WHAT IS
RADIATION?

57. They are electromagnetic waves
incapable of producing ions while
passing through matter due to
their lower energy.
UV RAYS is an example of
non-ionizing radiation

59. These radiations are X- rays. gamma rays
etc. DNA has so-called hotspots. where
mutations occur up to 100 times more
than the normal mutation rate. A hotspot
can be
at an unusual base, e.g.. 5-methylcytosine.
Ionizing radiations attacks on these hot
spot and break the DNA.

61. CHEMICAL MUTAGENS
Chemicals that cause changes to DNA sequence .

62. BASE
ANALOGUES
Molecules which have a very similar structure to one of the
four nitrogenous bases which are used in DNA (adenine,
guanine, cytosine or thymine).
A very common and widely used base analogue is
5-bromouracil (5-BU) which is an analogue of
thymine. The 5-BU functions like thymine and
pairs with adenine

63. Chemicals Changing the Specificity of Hydrogen
Bonding:
There are many chemicals that after
incorporation into DNA change the
specificity of hydrogen -bonding.
Those which are used as mutagens
are nitrous oxide (HNO2),
hydroxylamine (HA) and ethyl-
methane-sulphonate (EMS).

64. Nitrous
Oxide
(HNO2):
converts the amino group of bases into keto
group through oxidative deamination

65. Deamination of Adenine:
Results in formation of hypoxanthine, the pairing
behaviour of which is like guanine.
Hence, it pairs with cytosine instead of thymine replacing AT
pairing by GC pairing

66. Deamination of Cytosine:
Results in formation of uracil by replacing –
NH2 group with -OH group.
The affinity for hydrogen bonding of uracil is like
thymine; therefore, C-G pairing is replaced by U-A
pairing

67. Deamination of Guanine :-
Results in formation of xanthine, the later is not
mutagenic.
Xanthine behaves like guanine because there is no change in
pairing behaviour.
Xanthine pairs with cytosine. Therefore, G-C pairing is replaced by
X-C pairing.

68. Hydroxylamin
e (NH2OH):
It hydroxylates the C4 nitrogen of
cytosine.
Converts into a modified base via deamination which causes to base
pairs like thyamine.
GC pairs are changed into AT pairs.

69. Alkylating
Agents:
Addition of an alkyl group to the hydrogen bonding oxygen of
guanine (N7 position) and adenine (at N3 position) residues of DNA is
done by alkylating agents.
Following are some of the important widely used
alkylating agents:
(a) Dimethyl sulphate (DMS)
(b) Ethyl methane sulphonate (EMS) -CH3CH2SO3CH3
(c) Ethyl ethane sulphonate (EES) -CH3CH2SO3CH2CH3

70. CONTENTS
MUTAGENS
Made by
RUPAL TIWARI
DEAMINATING
AND ALKYLATING
AGENTS

71. Mutagens and their actions
RUPAL TIWARI

72.  Mutation
 Spontaneous Mutation & Induced Mutation
 Mutagen
 Chemical Mutagens
 Radiation
 Biological Mutagens
 Conclusion
Introduction

73. Mutagen
 A natural or human-made agent
which can alter the structure or
sequence of genetic material and
induce mutation .

74.  There are three main types of
mutagens classifying by their
sources
 Chemical Mutagens
 Radiation
 Biological Mutagens

75. • Transposable
element
• Ionizing
Radiation
• UV Radiation
• Base analogs
• Chemical
modification
agents
• Intercalating
agents
Biological
Mutagens
Radiation
Chemical
Mutagens

76.  Chemicals structurally resemble normal
bases, purines and pyrimidines
 Incorporate into DNA during replication
 Lead to incorrect insertion of nucleotides
opposite them in replication
Chemical Mutagens -Base analogs

77.  5-Bromouracil (5-BU)
 2-Aminopurine (2-AP)
For Example

78.  resembles Thymine (T)
 has Br atom at C-5 instead of methyl
group as in T
 can incorporate into DNA and pair with
either A or G due to tautomerization
5-Bromouracil
analog of a pyrimidine

79. * TAUTOMERIZATION – spontaneous structural alternations
between 2 forms, keto form and enol form
5-Bromouracil
analog of a pyrimidine

80. Mechanism of 5-
Bromouracil

81. Mechanism of 5-
Bromouracil

82.  Chemicals which alter structure and
pairing properties of normal bases
 Active on both replicating and non-
replicating DNA
 Result in mutation upon DNA replication
by forming baseless sites or mispair
 Two common chemical modification
agents
 Alkylating agents
 Deaminating agents
Chemical Mutagens-
Chemical modification agents

83. Alkylating agents
 Modify the normal bases by adding alkyl
groups
 Common alkylating agents
 Ethylmethane sulfonate (EMS)
 Nitrosoguanidine (NG)
 Di-(2-chloroethyl) sulfide (Sulfur mustard)
 Di-(2-chloroethyl) methylamine (Nitrogen
mustard)

84. Ethylmethane sulfonate (EMS)
Alkylating agents

85. Ethylate base’s 7-N & 6-O positions
Mechanism of
Ethylmethane sulfonate (EMS)

86. Ethylate base’s 7-N & 6-O positions
Mechanism of
Ethylmethane sulfonate (EMS)

87.  Oxidative deamination of amino
group in Adenine (A), Guanine (G)
and Cytosine (C)
Deaminating agents

88.  Nitrous acid (HNO2) is one of
common deaminating agents
 Convert the amino group (-NH2) into keto
group (=O)
 Change H-bonding potential of the
modified bases
Deaminating agents

89. Adenine (A) → Hydroxanthine
Mechanism of Nitrous acid

90. Cytosine (C) → Urail
Mechanism of Nitrous acid

91. Guanine (G) → Xanthine
Mechanism of Nitrous acid

92.  A group of aromatic organic
molecules
 Roughly the same dimensions as a
nitrogenous base pair
 Intercalate or wedge between the
base pair
Chemical Mutagens-
Intercalating agents

93.  Cause addition or deletion of base
pairs of intact DNA
 Alter reading frame of gene
 Result in non-functional gene
product
Chemical Mutagens-
Intercalating agents

94. Mechanism of
Intercalating agents

95. Mechanism of
Intercalating agents
 Common intercalating agents
 2,8-Diamino acridine (proflavin)
 Acridine orange

96. MADE BY
CONTENTS
 Detection of
mutation:
CIB method
 DNA repair
mechanism

97. DETECTION
OF
MUTATIONS

98. CIB METHOD
Primarily meant
to detect
radiation
induced
mutations
Also used to
detect
spontaneous
mutations

99. Three characters
C = Cross over
suppressor
B – Bar eye
I = Lethal
gene
On X chromosome

100. DNA REPAIR MECHANISM

101. Post Replication
RepairMismatch Repair
Photoreactive
Repair
Excision Repair
TYPES
SOS Repair

102. Mismatch repair

103. Why
•1 mistake in DNA base pairing
in 10,00,00,00,000 insertion
after the proofreading

104. HOW?
Insertion
Of Correct base
REMOVAL
Of Incorrect base
DETECTION
Of Mismatch

105. REMOVAL, SYNTHESIS AND SEALING
Exonuclease, Endonuclease, Polymerase, DNA ligase
DNA METHYLATION
Adenine Methylase
STRAND DISCRIMINATION
Recognition of newly synthesized strand as it has incorrect base pair
MECHANISM

107. •Crucial step
•Recognition of correct and incorrect
nucleotide
•Correct is on template strand and incorrect is
on newly synthesized strand
•Crucial because in it’s absence only 50% of
success rate is there.
STRAND DISCRIMINATION

108. •Enzyme- Adenine methylase
•It recognizes the substrate and
marks the newly synthesized strand
with incorrect base
•It marks by adding methyl group to each
of the Adenine residues during DNA
replication
DNA Methylation

109. REMOVAL, SYNTHESIS AND SEALING
REMOVAL
Endonuclease makes a nick on either side on
wrong base.
Exonuclease finally cleaves of the wrong base.
SYNTHESIS
DNA Polymerase fills in the gap using
the correct DNA strand as template.
SEALING DNA Ligase seals the gap.

110. POST REPLICATION
REPAIR

111. T=T DIMERS

112. A
B
C
D

113. ENZYMES
RecA
DNA
Polymerase
DNA
Ligase

114. Monomerization of T=T dimer by
various means

115. PHOTOREACTIVATION
REPAIR

116. Photolyase enzyme gets activated by the
absorption of blue light.

117. EXCISION REPAIR

118. EXCISION
REPAIR
Base excision
repair
Nucleotide
excision repair

119. BASE EXCISION
REPAIR

120. NUCLEOTIDE EXCISION
REPAIR

121. UvrA,
UvrB
Endonuclease: Recognizes
the damaged stretch
Exonuclease: Removes
the damaged strand
Endonucleases: Make 2 cuts on
either side of DNA strand
Synthesizes new
strand
Seals the end of newly
synthesized strand
UvrC
UvrD
DNA
Polymerase
DNA
Ligase

123. • Last resort, hence it’s name.
• TRANSLESON SYNTHESIS or EMERGENCY REPAIR
SYSTEM
• bacteria can induce the expression of about 20 genes
(including lexA, recA, and uvr) whose products allow DNA
replication to occur even in the presence of these lesions.
• Y family of DNA polymerases, synthesize DNA directly
across the damaged portion.
• Error prone synthesis, random nucleotide insertion.
• SOS repair itself might become mutagenic but prevents
organism from lethal mutation.

125. QUESTION TIME
Q1 What is missense mutation and nonsense mutation ?
Q2 What is euploidy ?
Q3 What is aneuploidy ?
Q4 Difference between pericentic and paracentric inversions?
Q5 What do you mean by mutagens ? Name the different types of mutagens.
Q6 What is alkylating agents ?
Q7 What is intercalating agents ?
Q8 What do you mean by base analogs ?