PPT about mutation

1. Mutation Breeding

2. Introduction :
 Mutation is a sudden heritable change in a
characteristic of an organism .
 Gene/Point mutation :- Mutation produced
by changes in base sequence of genes
Chromosomal mutation :- Mutation may be
produced by changes in chromosome
structure or even in chromosome number.
 Other terms- cytoplasmic or plasmagene mutation
 -bud or somatic mutation

3. Historical Account :
Hugo de Vries: 1900. introduced the term
“Mutation”.
Mutants were observed before this: e.g., short
legged sheep was discovered by an English
Farmer in 18th century. This sheep was used to
develop a breed-c/a Ancon.
Muller(1927)discovered the action of X-rays on
Drosophilla and Stadler discovered the effect of
gamma-rays in barley(H.vulgare) and
Maize(Z.mays).
Muller was awarded nobel prize in 1946

4. Historical Account :
 Auerbach and Robson-nitrogen mustards
produced mutation in Drosophila.
 subsequently a number of chemicals with
mutagenic action was discovered
 Mutation Breeding Programme was started
in Sweeden, USSR and Germany in 1927
after the discovery by Muller.

5.  Swaminathan is known as "Indian Father of Green
Revolution" for his leadership and success in introducing
and further developing high-yielding varieties of wheat in
India.
 Swaminathan and his team produced a mutant breed of
wheat by gamma irradiation of a Mexican variety (Sonora
64) resulting in Sharbati Sonora.
 The mutant variety Sharbati Sonora was officialy approved
in 1967. It was developed by irradiation of seeds with
gamma rays (200 Gy). Main improved attributes of mutant
variety are amber grain color, early maturity, bread and
chapati making and high protein content (16,5%).

6. Type of mutation
 Spontaneous (natural) mutation
 Frequency of mutation is one in 10 lakhs
 Different genes show different
mutation rate
 R-locus in maize mutate at a frequency
4.92x10-4, su at 2.4x10-6,Wx-highly stable.
 Rate of spontaneous mutation is affected by
genetic background and mutator gene

7.  Induced mutations- artificially induced by
certain physical of chemical mutagens
 Mutagens-agents used to induce mutation
 Mutation breeding -utilization of mutations
for crop improvement
 Induced mutation

8. General characteristics
 Generally recessive ,dominant also occur
 Generally harmful to the organism -most
cases-deleterious,some-beneficial
 Random-occur in any gene,some show
high rate
 Recurrent-same mutation can occur again
and again
 Induced mutations show pleiotropy due to
closely linked genes.

9. Effects of mutations on survival
 Based on the effect on viability mutations
are
Lethal-kill each and every individual
-dominant mutants do not survive
-recessive survive only heterozygous condition
Sublethal-kill more than 50% individual
Subvital-kill less than 50% individual
Vital-do not reduce the viability

10. Mutation
 A heritable change in the base sequence
of DNA
 Base mutation- change in a single base
position
 Transitions –purine Purine, (A-G,T-C)
pyramidine pyramidine (A-T or c,G-T or C)
 Transversions-purine- pyramidine,
pyramidine-purine
Affect one codon-affect one aminoacid in the
concerned protein
Substitution that generate codon that donot code
any aminoacid(nonsense codon-it acts as a
terminator of polypeptide chain)

11. Consequences of Mutation
 Silent Mutation---base change, no amino acid
change
 Neutral Mutation--- Base change resulting in a
change that does not affect protein function
– EX. Aspartic acid (D) Glutamic acid (E)
 Missense mutation---altered codon, new aa with
different chemical properties. Function affected.
 Nonsense mutation---base pair substitution
results in a stop codon (and shorter polypeptide)
 Frameshift mutations —additions or deletions.
Peptide may be longer or shorter.
 Sense mutation?

12. Chromosomal mutation
 Mutation associated with splitting and subsequent changes
in the structure of the chromosomes
 The end of the split chromosomes may fuse to form
structure again, but the new chromosomes are not always
exactly what the used to be
 The microscopic structures of chromosomes may be
characterized by deletion or deficiency (loss of a
chromosomal segment), duplication (doubling of a
chromosomal segment), inversion (rearrangement of a
group of genes in a chromosomal segment in a such a way
that their order is reversed; rearrangement of genetic
material in a chromosome results from loss of segment, its
rotation by 180°, and fusion of the separated ends) and
translocation (change in a position of a chromosome or
more often exchange of segments between different
chromosomes)

13. Genome mutation
Changes in sets of chromosomes
Remarks:
1. Breeders are more interested in gene mutation,
because chromosomal rearrangement usually
produce negative results, such as lower fertility of the
offspring
2. Mutant are aften of great value for breeding as
sources of new, previously unknown useful characters
3. Mutagenesis may be instrumental in obviating the
technical difficulties arising in the crossing of such a
small flowered crops such as millet

14. Effects Of Mutation :
 Lethal :- They kill each & every individual that carry them
in appropriate genotype .
 Dominant lethal : It can’t survive. Recessive lethal : kill in
homozygous state.
 Sub Lethal & Sub Vital :- Both mutation reduce viability but
don’t kill all the individual carrying them in appropriate
genotype.
 Sub Lethal : Kill more than 50%.
 Sub Vital : Kill less than 50%. Vital :- a) Don’t reduce the
viability. b) Crop improvement can utilize only such
mutations.


15. Mutation breeding

 The genetic improvement of crop plants for
various economic traits through the use of
induced mutations is referred to as mutation
breeding.
 Used in S.P. and clonally propagated crops.
 Eg:Wheat, Sugarcane


16. Mutation breeding is successful when……
:
 Desired variability exhausts in cultivated species
and germplasm.
 There is tight linkage between desirable and
undesirable traits.
 Only one or two characters are to be improved in a
fruit crop without changing its taste.
 Crop does not have sexuality, thus lacks
variability.
 The generation cycle is very long, such as
plantation crops, fruit trees….there mutation
breeding is the shortcut way for genetic
improvement. In ornamental plants Mutant Dog

17. Mutation breeding is successful
when…… :
 A particular reaction is to be blocked e.g., in
opium the synthesis of morphine takes place
in stepwise manner. If the reaction is
stopped at bane level, it will block the
synthesis of morphine without affecting the
conversion process of the bane into useful
pharmaceutical products. A B C D E H I J K
Enzyme1 Enzyme 2 Enzyme 4 Enzyme 5
Enzyme6 Enzyme 7 Enzyme 8 Enzyme 3


19. Induced Mutations
 Caused by exposure to a mutagen
 Causes
– Exposure to base analogs
– Chemical mutagens
– Intercalating agents
– Uv- radiation
– Transposable elements
– Mutator genes

20. Procedure for mutation breeding :
 Procedure for mutation breeding
Mutagenesis :- Treating a biological material
with a mutagen in order to induce mutation.
Irradiation :- Exposure of biological material
to one of the radiation(X-rays, gamma rays
etc.).
 Mutation Breeding: muations are induced for
crop improvement ,the entire operation of
the induction and isolation etc. of mutants

21. Selection of the variety for
mutagen treatment :
 Selection of the variety for mutagen
treatment Generally the variety selected for
mutagenesis should be the best variety
available in the crop.
 Note : In certain situations, it may be
desirable to isolate variants in varieties other
than the best one,
 e.g., Dwarf & semi dwarf mutants would
have to be isolated from tall varieties in
cereal crops (wheat, rice etc.)

22. Part of the plant to be treated :
 Seeds, pollen grains, buds/cuttings or
complete plant can be used for
mutagenesis.
 It depends on whether the crop is sexually
or asexually propagated & type of mutagen
to be used.
 Sexually propagated crops : Seeds are
commonly used because seed can tolerate
extreme environmental conditions.


23. Part of the plant to be treated
Clonal crops : Buds/cuttings are used for
mutagenesis.
Pollen grains are also infrequently used
because :-They are difficult to collect in
large quantities . Hand pollination(with
treated pollens) is rather difficult.
Survival percentage of pollens is relatively
low.
Note:- Pollen grains are the only plant part
which can be treated with ultra violet rays.

24. Dose and duration of the mutagen :
 The usefulness of a mutagen and its efficiency
depends on the mutagenic agent employed as
well as on specific characteristics of the biological
system to be treated.
 An optimum dose is the one which produce the
maximum frequency of mutation and causes
minimum killing.
 LD50 dose should be optimum
 LD5o-dose of the mutagen which kill 50% of the
treated individuals-varies from crop to crop.
 Vicia faba-46 krad Brassica napus oleifera-120-
140

25. Giving mutagen treatment
 selected plant is exposed to the desired dose
 Plants are immediately planted to raise the M1
 In the case of chemical mutagens,seeds are
usually pre-soaked with for few hours to initiate
metabolic activities,exposed to desired mutagen
and washed in running water for saurface dried
with blotting paper about to four hours to remove
the mutagen present in them

26. Procedure :

Treated seed/buds/cuttings Pollination with treated pollen are M1 Plants
M1 generation- Large no. of plants are grown in wider spacing. Dominant mutations are recorded
if any (generally mutations are recessive and do not express in M1) Chlorophyll sectors and
fertility is recorded. M1 plants are selfed and their seed is harvested separately.
Procedure M2-----Seed obtained from M1 is sown in wide spacing Selected
mutants are selfed. Oligogenic mutations are detected in M2 and are
harvested separately
M3-----M3 progeny is raised from selected M2 and evaluated for
homozygosity.
Selected homozygous M3 progenies are bulked together to conduct yield
trials in M4. M4-----M4 progeny are raised in replicated trials using local
check for comparison
M5-M9----Selected lines are tested in multiplication coordinated trials

27. Handling of mutagen treated population
 Number of mutations depends on the no. of
treated seeds-6000 seeds for 10 desired
mutation
 M2 size should be -1000-1500
 Monocots-primary tillers are good-arise from
shoot bud primordia present in the seed at
the time of mutagen treatment
 Dicots seeds produced in the main shoot
are show high frequency of mutations.

28. Procedure for Vegetative propagated
crops :
 In Veg. Prop. Crops mutations are
expressed in the form of chimeras.
 The chimera refers to genetically different
tissue in an individual.
 The individual has one type of tissue in one
part and another type of tissue in another
part.


29. Procedure for Vegetative propagated
crops :
 In apical buds, axillary buds and adventitious buds, there
are three functional layers, outer layer , inner layer and
middle layer
 L1-epidermis
 L2-part of leaf mesophyll and gametes.
 L3-rest of the plant body
 When the changes occur in entire inner or outer
layer, it is also known as Periclinal Chimera and
when only a part of inner or outer layer is altered,
it is called Sectorial Chimera.


31. Chimera ? :
Chimera - a plant or plant part composed of
genetically different layers
The most common example is a "variegated" plant
where different regions of the leaf are yellow or
white due to the lack of chlorophyll synthesis, i.e.
these are chlorophyll mutants. However, there are
many kinds of chimeras. Thornless blackberries
are chimeras where the L-I epidermis lacks the
ability to produce thorns.
Some fruits have sweet and sour regions of flesh,
which may be a chimera.


32. Chimera ? :
Mericlinal Chimera A
mutation occurs in one layer
and along the side of the
apex. Due to its position, the
cell division products of
those mutated cells occur as
a layer on only one side of
the plant. In other words,
only a section of one of the
layers is mutated. Mericlinal
chimeras are not stable.

33. Chimera ? :
Periclinal Chimera A
mutation occurs in one (or
more) layer at the top of the
apex. Due to its position, the
cell division products of the
mutated cells spread and
cover the entire layer of the
apex. In other words, the
entire layer is mutated.
Periclinal chimeras are stable
to very stable, and comprise
the most common type
chimeras in horticulture.

34. Chimera ? :
Sectorial Chimera A mutation
occurs in multiple layers at the
top of the apex.
In other words, an entire
section of the plant is
mutated.
Sectorial chimeras are stable to
very stable, and comprise the
most common type chimeras
in horticulture. Chimera ?

38. Sectorial chimera

40. Traditional Mutation Breeding Procedures
 Treat seed with mutagen (irradiation or
chemical)
 Target: 50% kill
 Grow-out M1 plants (some call this M0)
– Evaluation for dominant mutations possible, but most
are recessive
 Grow-out M2 plants
– Evaluate for recessive mutations
– Expect segregation
 Progeny test selected, putative mutants
– Prove mutation is stable, heritable

41. Mutation breeding scheme for
seed propagated crop
 Mutagenic application
 Growing the plants (M1 generation)
 Identification of induced mutation, seed harvest
from mutated plants (M2)
 Continue the identification and selection of
induced mutation (M3)
 First agronomic evaluation. Propagation of
promising lines (M4)
 Multilocation trials of stable mutant and
recombinant lines (M5 – M8)
 Official testing and releasing of mutant (M9)

42. Mutation breeding for oligogenic traits

43. Mutation breeding for oligogenic traits

44. Mutation breeding scheme for
vegetative propagated crop
 Mutagenic application
 Cutting back the M1V1 shoot, bud grafting, or in vitro
propagation via axillary buds
 Isolation of induced somatic mutation, establishment of
clones, cutting back of non-mutant shoots from chimeric
plants (M1V2)
 Further isolation of somatic mutations, vegetative
propagation of mutant plant (in vivo or in vitro), preliminary
evaluation of mutants (M1V3)
 Evaluation of mutant clone performance, assesing
segregation from mutant crosses and reselection of
desired recombinants. Released of improved mutant
(M2V4)

45. Application of mutation
breeding :

 Induction of desirable mutant alleles which
may not be present in the germplasm
available to the breeder.
 In improving specific characteristics of well
adapted high yielding variety .
 Mutagenesis has been successfully used to
improve various quantitative characters
including yield.

46. Limitations :
 Limitations The frequency of desirable
mutants is very low.
 Desirable mutations are commonly
associated with undesirable side effects.
 There may be problems in the registrations
of a mutant variety.
 Mutations in quantitative traits are usually in
the direction away from the selection history
of the parent variety.
 Most of the mutations are recessive