2. Wh at is M u tation ?
Sudden heritable changes in genetic material is know as Mutation
The term Mutation refers both to
•Change in genetic material &.
•To the process by which the change occurs.
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3. With ou t M u tation
•All genes would exist in one form
•Alleles would not exist
•Genetic analysis would not be possible
•Not able to evolve & adapt to environmental
changes
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4. D N A S e qu e nce s
At molecular level, mutations are alteration in the DNA molecules.
Chromosomes can exchange parts & genetic material can even jump from
one to another chromosomes
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5. S om atic M u tation
•Somatic mutation •Germline mutation
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Cancer
6. G e rm line M u tation
In germline mutation, the change occurs during the DNA replication that
processes meiosis. The resulting gametes & all the cells that descend from
it after fertilization have the mutation 6
7. C las s ification
There are different ways of classifying mutation
Functionally Structurally Nonsense
Point Missense
Frameshift Silent
Harmful Neutral
Beneficial
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8. H arm fu l m u tation
Mutation can cause errors in protein sequence creating non functionally
proteins. Harmful mutation can cause genetic disorders
•,Drosophila melanogaster A drosophila with legs grown over the head as
a result of mutation.
•A baby with an abnormal formation of eyes and eyelids because of mutation.
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9. Be ne ficial M u tation
•Ultimate source of all genetic variation
•Raw material for evolution
•able to evolve & adapt to environmental changes
For example
•Protection against HIV infection
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10. N e u tral M u tation
A neutral mutation is a mutation that occurs in an amino acid
codon but it has no impact.
A change in a base pair results in an amino acid change but the new
amino acid has the same chemical properties as the old amino acid.
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11. S tru ctu rally
Point Nonsense
Frameshift Missense
Silent
A point mutation or single base
substitution, is a type of mutation that
causes the replacement of single base
nucleotides with another nucleotides of
DNA or RNA
12. S tru ctu rally
DNA structure permits some basic type of alteration or mutation at a
site. Point mutation can be categories as
Transition
Deletion Transversions
Insertion Translocation
Inversion
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14. P oint M u tation
Translocation are transfer of a Piece of One chromosomes to a non
homologous chromosomes
Translocation can alter the phenotype in several ways
•The break may occur within a gene destroying its function
•Translocated genes may come under the influence of different
promotes and enhance so that their expression is altered
•Breakpoint may occur within a gene creating a hybrid gene.this
may be transcribed & translated .
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15. P oint M u tation
Replacement of a Purine base with another Purine or pyrimidines
with another pyrimidines
Replacement of a purine with pyrimidines or vice versa
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16. P oint M u tation
A point mutation can also change a codon so that a different protein is specified,
a non synonymous change.
For example Sickle Cell disease
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17. D N A s tru ctu re
A nonsense mutation is a genetic mutation in a DNA sequence that results
in a shorter, unfinished protein product
During protein formation,DNA nucleotide sequences are read three
nucleotides “Codon” & each codon corresponds to a specific amino acid
or stop codon, also called nonsense codon
Thus ,nonsense mutation occurs when a premature or stop codon is
introduced in DNA .When the mutated sequence is translated into a
protein, the resulting protein is incomplete & shorter than normal. Most
nonsense mutation result in non functional protein
Examples:
•Blood Clotting disorder
•Becker Muscular Dystrophy
•Ehlersdanles Syndrome
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18. Sense mutations are the opposite of nonsense mutations. Here, a stop
codon is converted into an amino acid codon. Since DNA outside of
protein-coding regions contains an average of 3 stop codon per 64, the
translation process usually stops after producing a slightly longer protein.
Example: Hb-α Constant Spring. alpha-globin is normally 141 amino
acids long. In this mutation, the stop codon UAA is converted to CAA
(glutamine). The resulting protein gains 31 additional amino acids
before it reaches the next stop codon. This results in thalassemia, a
severe form of anemia.
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19. P oint m u tation
Frameshift mutation is a genetic mutation caused by indels i.e., insertion
or deletion of a number of nucleotides.
Due to triplet nature of gene expression by codon, the insertions or deletion
can disrupt the reading frame
A Frameshift mutation causes the readings of all codon after the mutation to
the different amino acids .the protein being created could be abnormally
short ,long or contain the wrong amino acids.and functionless.
Example:
Tay sachas disease
20. A mutation can occur spontaneously or be induce by chemicals or radiation
Spontaneous mutations on the molecular level include:
Tautomerism - A base is changed by the repositioning of a hydrogen atom.
21. Depurination - Loss of a purine base (A or G).
Deamination - Changes a normal base to an atypical base; C → U,
22. Replacement of a Purine base with another Purine or pyrimidines
with another pyrimidines
Replacement of a purine with pyrimidines or vice versa
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23. Induced mutation are those resulting from exposure of organism to mutagenic
agents such as ionizing radiation UV light or various chemical.
Induced mutations on the molecular level can be caused by Chemicals
•Hydroxylamine NH2OH
•Base analog i.e., Brdu
•Alkylating agents
•DNA intercalating agents e.g. ethidium bromide
•DNA cross linkers
•Oxidative Damage
•Nitrous Acids
•Acridines Dyes
25. Radiation
e.g., X-rays, UV
Ionizing radiation breaks covalent bonds including those in DNA and is the
leading cause of chromosome mutations. Ionizing radiation has a cumulative
effect and kills cells at high doses.
UV (254-260 nm) causes purines and pyrimidines to form abnormal dimer
bonds and bulges in the DNA strands.
26. In some genes mutation are more likely to occur in region called hotspots,
where sequences are repetitive. It is as if the molecules that guide and carry
out replication become confused by short repeated sequences.
For example:
More than one third of the many mutation that causes Alkaptonuria
occur at or near one or more CCC repeats even though these repeats
accounts for only 9% of the gene
Such a segment of DNA with identical sequences but opposite in direction is
called a palindrome. A palindrome site is a sequence of base pairs in double
stranded DNA that reads the same backwards and forward across the double
strand.
27. P re p are d B y
ZAH ID A U MAR
B .S c H ons, 5th se m e te r
387-B H -07
D e p t of E nvironm e ntal S cie nce s
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