mutation and its evolutionary significance.

1. MUTATIONS & THEIR
EVOLUTIONARY SIGNIFICANCE
Submitted to,
Dr. Chandini V.K
Assistant professor
Dept of botany
St Teresa’s college
Ernakulam
Submitted by,
Silpa Selvaraj
Roll no: 14
I Msc Botany
St Teresa’s college
Ernakulam
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2. Oh god, where
are my body
hairs!!!
2

3. How did it
become white in
colour??
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4. 4

5. Is it because of
any disease??
Is it
mutation??
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6. MUTATION
• Mutations are the sudden heritable changes that
occur in the genetic material of an organism.
• Mutations are the main cause of diversity in
organisms.
• Mutations can have positive, negative as well as
neutral effects.
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7. HOW DO MUTATIONS OCCUR?
• DNA is made up of four bases:
• Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).
• Human DNA contain over 3 billion base pairs that are combined in
different sequences.
• These base sequences contain the instructions for making
proteins.
• When these base sequences are changed, it results in mutation.
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8. CAUSES OF MUTATION
• Mutations may occur due to various causes.
• Some mutations are spontaneous without any outside influence. They
occur when errors occur during DNA replication.
• Some mutations are caused by environmental factors.
• Any environmental factor that causes mutation are called mutagens.
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10. SIGNIFICANCE OF MUTATIONS
• No. Obviously large scale changes are going to
have a significant effect.
• Many single base mutations most likely have no
effect, unless they change the reading frame.
• Imagine the coding sequence TAC CCC GGG. It
transcribes into the following mRNA: AUG GGG
CCC, which would translate into start-glycine-
proline. As glycine is encoded by four codons
(GGG, GGA, GGC, GGU), any change in the third
position of that codon will have no effect.
Are all
mutations
bad??
Are all
mutations
bad??
What about
single base
changes
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11. TYPES OF MUTATION
1. Positive mutations:
• These mutations cause changes in the DNA that give rise to new trait that actually
gives the organism an advantage.
• The advantage a beneficial mutation provides the organism, is passed from
generation to generation, increasing chances for the offspring to survive.
1. Eg: Mutations that lead to antibiotic resistance in bacteria, Humans have
trichromatic vision, we can discriminate between three colours: red, green and
blue. Many animals have dichromatic or monochromatic vision and lack the ability
to perceive all the colors we can. This ability is likely the result of a beneficial
mutation that occurred in our DNA several million years ago.
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12. 2. Negative mutations:
• Negative mutations are disadvantageous and harmful to the organisms.
• It can cause several genetic disorders or abnormalities.
• A human example is cystic fibrosis. A mutation in a single gene causes
the body to produce thick, sticky mucus that clogs the lungs and blocks
ducts in digestive organs.
• Sickle cell anaemia: Causes the RBC to acquire sickle like shape,
making it difficult for the Hb cells to carry oxygen and also the affected
individuals are at high risk of heart attack, strock etc.
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13. 3. Neutral mutations:
• Neutral mutations are changes in DNA
sequence that are neither beneficial nor
detrimental to the ability of an organism to
survive and reproduce.
• Eg : Silent mutations. They are neutral
because they do not change the amino
acids in the proteins they encode.
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14. The variation seen among insects shown here are
a result of variations in DNA sequence.
The variation of hair, skin colour, and height seen in
these individuals are result of mutations.
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15. Germline mutations
• Occur in the sex cells or gametes.
• These mutations can be passed to the next generation.
• If the zygote contains the mutation, every cell in the resulting organism will
have that mutation.
Somatic mutations
• Occur in other cells of the body.
• These mutations are confined to just one cell and its daughter cells.
• Somatic mutations cannot be passed to offsprings.
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16. Germline mutation Somatic mutation
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17. EVOLUTION
• Evolution refers to the process by which living organisms change over time through
changes in the genetic material.
• Such evolutionary changes result from mutations that produce genetic variation,
giving rise to individuals whose biological functions or physical traits are altered.
• Those individuals who are best at adapting to their surroundings leave behind more
offspring than less well-adapted individuals.
• Thus, over successive generations (in some cases millions of years), one species
may evolve to take on divergent functions or physical characteristics or may even
evolve into a different species.
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18. MUTATION & EVOLUTION
• Complete set of alleles in a species or population is called gene pool.
• Mutation create variation in the gene pool and it can be considered as the the first
step of evolution .
• Population with large gene pool are said to be genetically diverse and very robust.
• Not all mutations lead to evolution.
• The only way for a mutation to influence the gene pool is, if it can be passed on to
the next generation.
• For this to happen, the mutation must occur in the sex cells or the gametes.
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19. • If the mutation is beneficial to the organism, it will be able to survive and
reproduce successfully, passing the mutated gene to the offsprings as well.
• If the mutation is harmful to the organism, it will not be able to survive and
reproduce.
• Thus by natural selection, individuals having non beneficial or harmful
mutations are removed from the population .
• Individuals having favourable or beneficial mutations tend to accumulate in that
population resulting over time in evolution.
• That is, without any change in gene pool, without any new alleles added due to
mutations, evolution cannot occur.
• Thus genetic variation is the driving force of evolution.
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21. MUTATION THEORY OF EVOLUTION –
HUGO DE VRIES(1901)
• Hugo de Vries, a Dutch botanist, offered theory of
mutation.
• According to De Vries, new species are not formed
by a slow and gradual process. Instead, new
species arise all at once through saltation.
• Saltations are one step sudden and large scale
mutations.
Hugo De Vries
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22. EXPERIMENT
• His mutation theory was based on his observations on the plant,
evening primrose, Oenothera lamarckiana .
• He noticed sudden changes between generations. For example,
he noted that most of the offsprings looked like the parent, but
some looked different, with different stem height, flower colour,
leaf shape etc.
• He called these changes undergone from one generation to the
next as mutations.
• De Vries wondered if these ''sudden mutations'' could be passed
on to the next generation. So he bred the plants, and he found
that their offsprings indeed also had the mutations.
• Because these plants kept the mutations, he considered them to
be brand new species.
Evening primrose
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24. Evolution of new species is not a continuous
process, but is the result of sudden, discrete and
discontinuous changes in the existing species.
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25. MAIN POSTULATES OF MUTATION THEORY
• Mutation is the raw material for evolution.
• Mutations are heritable and form new species.
• Mutations arise suddenly in one step and not gradually.
• Mutations occur in all possible directions.
• Intermediate forms are not formed because new species are formed by sudden
changes.
• Unsuitable and unfavourable mutations would be eliminated by natural selection.
• Single step large mutations which can give rise to new species are called saltations.
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26. EVIDENCES FOR MUTATION
THEORY
• Appearance of short legged sheep variety called Ancon sheep, from long
legged parents in single generation.
• Appearance of hornless variant of hereford cattle from horned parents in
single generation.
• Origin of hairless cats, dogs and mice.
• Origin of new plant varieties. Eg: red sunflower.
• Eye colour in drosophila.
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27. Ancon sheep Hereford cattle
with no horns Hairless cat and dog
Red sunflower
Red and white eyed
drosophila
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28. SIGNIFICANCE OF MUTATION THEORY
• It was the first extensive theory to explain ;
1. Importance of mutation in evolution.
2. Experimentally demonstrated the process of mutation. ( His experiment on
Oenothera lamarckiana).
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29. CRITICISMS AGAINST MUTATION THEORY
• It appears impossible to explain the discontinuity among individuals, by
supposing that each member has appeared suddenly due to mutations.
• It is difficult to believe that mutations have provided sufficient opportunity for
all specialized adaptations that exist in nature.
• Mutations cannot explain the presence of flightless birds in oceanic islands.
• D.M Davis discredited the whole work of De Vries by claiming that Oenothera
lamarckiana is of hybrid origin, which produced various varieties.
• The mutations in evening primrose are essentially the variations in the
chromosome number.
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30. • The rate of mutation is very low (say it occurs in one out of a few million
genes). In that case, it is hard to explain how mutations could have such a
significant impact on evolution.
• Most of the mutations are negative.
• This theory could not explain the role of nature.
• It could not explain the process of mimicry, protective colouration, mutual
dependence of flowers and pollinating insects.
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31. REFERENCE
• Barraclough, T.G. (2019).The evolutionary biology of species.
Imperial publications.
• Gilchrist, D.A.(2022,September 6).Mutation. National human genome
rice research. https://www.genome.gov/geneticsglossary/Mutation
• Ridley, M.(1993).Evolution. Blackwell publications.
• Singh, S.P.(2000).Evolutionary biology. Rastogi publications.
• Yang, B.& Rifkin, S.A.(2020,October 14). Mutations: A larger target
leads to faster evolution. Elife. https://doi.org/10.7554/eLife.62689
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32. THANK YOU