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Presented by :- Rajesh Kumar(152122028) Raju Kumar Singh(152122029)

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Mutation

Mutation is a change of the nucleotide sequence of the genome of an organism, virus, chromosomal DNA and other genetic element.

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• Mutations may be harmful.• Mutations may be beneficial.• Mutations may have no effect on the organism.

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Types of Mutation• Substitution• Insertion• Inversion• Deletion

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SubstitutionA substitution is a mutation that exchanges one base for another (i.e., a change in a single "chemical letter" such as switching an A to a G).

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InsertionInsertions are mutations in which extra base pairs are inserted into a new place in the DNA.

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Inversion• An inversion is a chromosome rearrangement in which

a segment of a chromosome is reversed end to end.

• An inversion occurs when a single chromosome undergoes breakage and rearrangement within itself.

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Deletions are mutations in which a section of DNA is lost, or deleted during DNA replication.

Deletion

A mutation can occur spontaneously or induced by chemicals or radiations.

Spontaneous mutations on the molecular level include:

Tautomerism - A base is changed by the repositioning of a hydrogen atom.

Causes of Mutation

Spontaneous Mutation

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Depurination - Loss of a purine base (A or G).

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Deamination - is the removal of an amine group from a nucleotide. Changes a normal base to an atypical base; C → U,

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Replacement of a Purine base with another Purine or pyrimidines with another pyrimidines.

Replacement of a purine with pyrimidines or vice versa.

Transition -

Transversions -

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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 cross linkers•Oxidative Damage•Nitrous Acids

Induced Mutation

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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.

Radiation

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Mutation in Humans

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Down Syndrome• Also known as trisomy 21, is a genetic disorder

caused by the presence of all or part of a third copy of chromosome 21.

• It is typically associated with physical growth delays, characteristic facial features and mild to moderate intellectual disability.

• The average IQ of a young adult with Down syndrome is 50, equivalent to the mental age of an 8 or 9 year old child.

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Edward’s syndrome• Also known as Trisomy 18 [T18] is a chromosomal

disorder caused by the presence of all or part of an extra 18th chromosome.

• Named after John Hilton Edwards, who first described the syndrome in 1960.

• Many parts of the body are affected. Babies are often born small and have heart defects. Other features include a small head, small jaw, clenched fists with overlapping fingers.

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Patau syndrome• It is a syndrome caused by a chromosomal

abnormality, in which some or all of the cells of the body contain extra genetic material from chromosome 13.

• The extra genetic material from chromosome 13 disrupts the normal course of development, causing multiple and complex organ defects.

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We are very thankful to Dr. Lal Mohan Kundu Sir for giving us this opportunity.