Khushboo Arya 2018013626 B.sc. Agriculture 1 Year

Khushboo arya 2018013626

B.Sc. Agriculture 1st year

What is mutation ? Mutation

is phenomenon which results in alternation of DNA sequences and consequently results in changes in the genotype and the phenotype of an organism.

Induced mutation 

Mutation induced in an organism by treatment with physical or chemical mutagens are called induced mutation. The agents which are used to induce mutation are called mutagens. Certain genes in an organism promote the mutation of other genes nearby in an organism promote the mutation of other genes nearby in the chromosomes.

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For example the Dt gene in chromosome number 9 of maize increases mutation rate of other genes .

What is mutagens ? 

Agents which causes mutation in the organism is called mutagens.

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There are different classes of mutagens based on their chemical or physical properties.

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All these mutagens induce mutations in genome by structural or chemical modification of genetic material (DNA).

Physical mutagens The different types of radiations having mutagenic properties are known as physical mutagens.

Radiations radiations are grouped into two classes depending on the kind of effects they have on the atoms in their path: a) Ionizing

b) non-ionizing

Chemical mutagens 

The first report of mutagenic action of a chemical was in 1942 by charlotte auerbach, who showed that nitrogen mustard could caused mutations in cells.

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Since that time, many other mutagenic chemicals have been identified and there is huge industry and government bureaucracy dedicated to finding them in food additives, industrial waste, etc.

 1.

base analogs

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These chemicals structurally resemble purine and pyrimidines and may be incorporated into DNA in place of the normal bases during DNA replication.

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2. chemicals which alter structure and pairing properties of bases

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- nitrous acid

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- methyl methanesulfonate

3. intercalating agents  Acridine orange, proflavin, ethidium bromide. 

 All

are flat, multiple ring molecules which interact with bases of DNA and insert between them. This insertion causes a “stretching” of DNA duplex and the DNA polymerase is “fooled” into inserting an extra base opposite an intercalated molecule. The result is that intercalating agents cause frameshifts.

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