1. Mutations are changes in the nucleotide sequence of DNA that may occur in somatic or germ cells. Most mutations are neutral or harmful, but some may provide benefits. 2. Mutations arise from errors in DNA replication or distribution that result in heritable changes to organism characteristics. Gene and chromosomal mutations can both produce phenotypic effects. 3. Mutations are caused by physical mutagens like radiation or chemical mutagens like alkylating agents and deamination agents. Common chemical mutagens include EMS, MMS, and sodium azide.

1. Mutation- Origin, Types, Dose
And Parts for Application
Dr. Sujit Ghosh
J K College
Purulia

2. Introduction
1. Changes in the nucleotide sequence of DNA
2. May occur in somatic cells (aren’t passed to offspring). May occur in gametes
(eggs & sperm) and be passed to offspring
3. Mutations happen regularly. Almost all mutations are neutral Chemicals & UV
radiation cause mutations Many mutations are repaired by enzymes
4. Some type of skin cancers and leukemia result from somatic mutations Some
mutations may improve an organism’s survival (beneficial)
5. The replication and distribution of genetic material is extremely accurate so
that the genetic information is usually passed on from one generation to the
next without alteration.
6. But, occasionally errors do occur both during replication and distribution of
the genetic material giving rise to sudden heritable changes in the characters
of organisms .
7. such alterations are called mutations , while individuals showing these
changes are known as mutants.
8. A mutations may arise due to a change in the base sequence of a gene. Such
mutations are called as gene mutations or point mutations.
9. But changes in chromosomal number and structure also produce heritable
changes in phenotype; these are termed as chromosomal mutations.

4. Phenotypic effects
1. Morphological mutations are mutations shows the outwardly visible properties of
an organism (i.e. curly ears in cats)
2. Lethal mutations are mutations that affect the viability of the organism (i.e. Manx
cat).
3. Conditional mutations are mutations in which the mutant allele causes the mutant
phenotype only in certain environments (called the restrictive condition). In the
permissive condition, the phenotype is no longer mutant. (i.e. Siamese cat – mutant
allele causes albino phenotype at the restrictive temperature of most of the cat body
but not at the permissive temperature in the extremities where the body
temperatures is lower).
4. Biochemical mutations are mutations that may not be visible or affect a specific
morphological characteristic but may have a general affect on the ability to grow or
proliferate.
a) Most microorganisms are prototrophs which means that they can grow on a
simple growth medium including an energy source and inorganic salts. Biochemical
mutations include those that affect proteins or enzymes required to grow on various
nutrients or to synthesize various components. Thus, these mutations cause the
microorganisms to become auxotrophs (they must be supplied with additional
nutrients if they are to grow). For example, the bacterium Escherichia coli does NOT
require the amino acid tryptophan for growth because they can synthesize
tryptophan. However, there are E. coli mutants that have mutations in the trp genes.
These mutants are auxotrophic for tryptophan, and tryptophan must be added to the

6. 1.Mutation are mainly occurs in
recessive genes compared to
dominant genes.
2.Most of the mutation are harmful to
plants, but few are used as helpful
used in economic traits.
3.Mutations are recurrent.
4.Induced mutation are linked.

10. Class Mutagen
Physical mutagens
1.Ionizing radiations
-particulate radiations
-non-particulate radiations
2.Non-ionizing radiations
-Alpha ,beta ,fast neutrons, thermal
neutrons
-X-rays, gamma rays
-UV rays
Chemical mutagens
1.Alkylating agents
-base analogues
-acridine dyes
2.Deamination agents
-other chemical mutagens
-mustard gas, nitrogen mustard,
EMS,MMS,EES.
-5-bromouracil,2-amino purine
-acriflavin,proflavin,acridine orange.
-nitrous acid (HN02)
-hydroxylamine, sodium azide.
EMS-ethylmethane sulphonate,
MMS-methylmethane sulphonate,
EES-ethylene sulphonate.
Mutagen