1. MUTATION
Presentation by
P.KATHIRAVAN
M.Sc.,(Agri) Genetics and Plant Breeding

2.  HISTORY OF MUTATION
 1929- First proof of induced mutations in plants ; radium ray
treatment of Datura stromanium (Gager and Blakeslee).
 1927 – H.J.Muller working with Drosophila provides proof of
mutation induced by x-rays, Muller champains induced
mutation for animal and plant breeding and opens a new era in
genetics and breeding..

3.  1928 – Stadler publishes the first result of mutation induction
in crop plants, barley , wheat, maize ,oats etc.,
 1936- The first induced mutant variety is released ,tobacco
variety – ‘chlorina’ using x-rays in Indonesia .
 1944- First reports of chemical induced mutation by Auerbach
and Robson.

4. MUTATION
 Mutation is a sudden heritable change in a characteristic of an
organism.
 A mutation may be the result of a
 change in a gene,
 a change in chromosome(s)
 that involves several genes or
 a change in a plasma gene/
 genes present in the cytoplasm.
eg., In chloroplasts, mitochondria, etc.,

5.  Mutations have certain general characteristics (RRR)
 Mutations are generally recessive but dominant mutations
also occur.
 Mutations are random i.e ., they may occur in any gene.
However, some genes show higher mutation rates than others.
 Mutations are recurrent that is, the same mutation may occur
again and again.
 Induced mutations commonly show pleiotropy, often due to
mutations in closely linked genes.

6.  “PLEIOTROPY” refers to the phenomenon in which a single
locus affects two or more apparently unrelated phenotypic
traits.

7.  Mutations are generally harmful to the organism. Most of the
mutations have deleterious effects, but a small proportion
(Ca0.1%) of them are beneficial.

8.  CLASSIFICATION OF MUTATION
 I) BASED ON SIZE
 1.Point Mutation - A point mutation occurs in a genome when
a single base pair is added, deleted or changed (base pair
substitution, insertion or deletion).
 Frame shift mutation – It is due to deletion or insertion of a
base sequence, so that there will be a change in amino acid.

10. 2. Gross Mutation
• Changes involving more than one nucleotide pair, may
involve the entire gene, the entire chromosome, or sets of
chromosomes (polyploidy).
 II.) BASED ON QUALITY
 (A) Structural Mutation: Changes in the nucleotide
content of the gene.
 Substitution mutation – Substitution of one nucleotide for
another.

11.  a. Transition mutation substitute one purine for another or one
pyrimidine for another.
 b. Transversion mutation substitute a purine for a pyrimidine
or vice versa.
 (B) Rearrangement Mutation:
 Changing the location of a gene within the genome often
leads to “position effects”.

12.  1. Within a gene
 Two mutations within the same functional gene can produce
different effects, depending on whether they occur in the cis or
trans position.
 2. Moving the gene locus
 It may create new phenotypes, especially when the gene is
relocated near heterochromatin.

13.  a. Translocation – movement to a non-homologous
chromosome.
 b. Inversion – a portion of the DNA sequence is excised then
reinserted at the same position but in the opposite orientation.
 III. BASED ON ORIGIN
 (A) Spontaneous mutation: Occurs naturally and is of
unknown origin. It is also known as background mutation. It
occurs at a frequency of 10-6 .

14.  (B) Genetic control: The mutability of some genes is known
to be influenced by other ‘mutator genes’.
 1. Specific mutator – It affects one locus.
 2. Nonspecific mutator – It simultaneously affects many loci.
 (C) Induced mutation: Mutations produced due to the
treatment with either a chemical or a physical agent are called
as induced mutation.

15.  The agents capable of inducing mutations are known as
mutagens.
• Mutation induction rarely produces new alleles; it produces
alleles, which are already.
 known to occur spontaneously or may be discovered if an
extensive search were made.
 It is reasonable to say that induced mutations are comparable
to spontaneous mutations in their effects and in the variability
they produce.

16.  But the induced mutations have a great advantage over the
spontaneous ones; they occur at a relatively higher frequency
so that it is practical to work with them.
 Mutagens
 Agents that induce mutations are known as mutagens.
 Mutagens may be different kinds of radiation (physical
mutagens) or certain chemicals (chemical mutagens).

17. TYPES OF MUTAGENS:
 A. Physical mutagens
(all of them are various kinds of radiation) .
 1. Ionizing radiation
a. Particulate radiation.
 eg. α – rays (DI), β- rays (SI), fast neutrons* (DI),
and thermal neutrons (DI).

19. b. Non Particulate radiation
(electromagnetic radiation),
 eg., X- rays* (SI), and γ- rays (SI).
 DI - densely ionizing
 SI - sparsely ionizing radiations.
 2. Non Ionizing radiation.
 eg. UV radiation.

20.  B. Chemical mutagens
 1. Alkylating agents
 e.g., Sulphur mustard, Nitrogen mustards,
 Epoxides, Imines, (e.g, ethylene imine or EI)*,
 Sulphates and sulphonates, Diazoalkanes,
 Nitroso compounds, e.g., N-methyl-N-nitro-N′-
nitrosoguanidine (MNNG)

22.  2. Acridine dyes
 e.g., Acriflavine, Proflavine ,
 Acridine orange, Acridine yellow,
 Ethidium bromide.
 3. Base analogues
 e.g., 5- bromouracil, 5-chlorouracil.

23.  4.others
 e.g., Nitrous acid, Hydroxyl amine, Sodium azide*.
 (* denotes that these agents are commonly used in mutation
breeding).

24. GAMMA GARDEN
• Gamma garden or Atomic garden is a concept popularized
after the Word War 2 for the peaceful use of atomic energy
(atoms for peace) for the crop improvement.
• Gamma gardens are first started in Long Island, New York,
USA.
• In India Gamma garden was 1st started in Bose Research
Institute, Culcutta in 1959.

25.  Gamma gardens or Atomic gardens are a type of induced
mutation breeding where radioactive sources particularly
gamma rays from cobalt -60 or Caesium-137 are used to
induce desirable mutations in crop plants.

26.  Former Atomic Gardening Society President Muriel Howorth
shows popular garden writer Beverley Nichols a two-foot-
high peanut plant grown from an irradiated nut in
her own backyard.

27.  Primary research center and Institutes in India that
participated in the development and release of various
mutants;
 Indian Agricultural Research Institute ( IARI) - New Delhi
 Baba Atomic Research Center - Mumbai
 Tamil Nadu Agricultural University - Tamil Nadu
 National Botanical Research Institute - Lucknow , UP