EPIGENETICS by SANJEEVKUMAR DPT.OF GENETICS AND PLANT BREEDING UAS GKVK BENGALURU.

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EPIGENETICS
SANJEEVKUMAR
PALB 6252
Jr.MSc.
DEPARTMENT OF GENETICS AND PLANT
BREEDING.
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3. QUESTIONS ?????
1.HOW EMBRYONIC STEM CELLS DIFERENTIATE INTO
NERVE CELL,BRAIN CELL ,HEART CELL etc. WITH
DIFFERENT FUNCTIONS,EVEN THOUGH ALL CELLS
CONTAIN SAME DNA ?
2.WHY ONE IDENTICAL TWIN SUFFER FROM
DISEASE(CANCER) AND OTHER DOESN’T ?
3.WHETHER OUR LIFE STYLE CAN INFLUENCE OUR
CHILDREN AND GRANDCHILDREN GENOTYPE….?
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4. CONT…
4. WHETHER WE CAN CONTROL OUR DNA.?
5.WHY DO PLANTS BLOOM IN ATUMN BUT NOT IN
WINTER.
6.WHETHER LAMARK WAS 100% WRONG ???
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5. Epigenetics
• The term EPIGENETICS coined by
- Waddington in 1942.
• Epigenetics literally means “above”
Or “ on top of” genetics.
• All genetic modification s excluding change in DNA.
“CHANGE IN PHENOTYPE WITHOUT CHANGE IN
GENOTYPE.”
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7. A. TATACATGCACC
B. TATACTTGCACC
C. TATACATGCACC
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Phenotype
Phenotype
Phenotype
m m
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Epialleles
are alleles of a locus which have
identical DNA sequences but
display different epigenetic
states, and which have been
proposed to influence a variety of
phenotypes in plants and animals
(Richards 2006).
Epigenomics-
Global analyses of epigenetic
changes across the entire
genome.
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1.How embryonic cell
differentiate ?
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Brain Heart Nerve

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Brain Heart Nerve

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Nerve

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(Tumour repressor gene in
cancer. )
2.Why one identical twin suffer from disease and other one doesn't ?
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16. MECHANISMS
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• DNA methylation
• Histone modifications
Acetylation
 Methylation
 Phosphorylation,
Ubiquitination
• RNA mediated
interference

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The resulting 5-methyl cytosine (5mC) is often repressive and can lead to gene
silencing (Cedar and Bergman 2012).
The repressive nature of 5mC is thought to inhibit the binding of DNA by transcription
factors (Watt and Molloy 1988) or to recruit additional chromatin proteins to form
heterochromatic state that is inaccessible for transcription.
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18. Cytosine methylation in plants occur in the
contexts of :
 CG
 CHG
CHH (H=A, C or T)
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19. MAINTENANCE METHYLATION
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20. HISTONE MODIFICATIONS
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21. Histone Acetylation & Deacetylation
 Histone acetylation
– Histone acetyl transferases (HATs)
 Adds acetyl groups to histone tails
 Reduces positive charge and weakens interaction of histones
with DNA
 Facilitates transcription by making DNA more accessible to
RNA polymerase II
 Histone deacetylation
 – Histone deacetylases (HDACs)
 Removes acetyl groups from histone tails
 Increases interaction of
DNA and histones
 Represses transcription
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22. Effects of Acetylation
• -ve charge on histone
• reduces affinity of tail for adjacent nucleosomes
• creating a transcription permissive environment
• increase the access of transcription factors
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23. Histone Methylation
 Histone methylation
• Histone methyl transferases (HMTs)
– Histone lysine methyl transferases(HKMTs)
Methylate lys (k) residues
• Protein argenin methyl transferase (PRMTs)
Methylate arge(R) residues
• Methylation can result in activation or repression of expression
 Trimethylation of histone H3 at lysine 4 (H3K4) is an active mark
for transcription
 Dimethylation of histone H3 at lysine 9 (H3K9), a signal for
transcriptional silencing
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25. Effects of Histone methylation
• Methylation does not neutralize charge but recruit silencing
or regulatory proteins that bind methylated histones.
• transcription repression
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Fig. Different modifications of histones lead to different states of chromatin architecture,
which affects gene expression.13-01-2017

27. PHOSPHORILATION
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•Phosphorylation increase the negetive charge
on Heston as a result less interaction betwen
DNA and Histones.
chromatin decondensation.
•Dephosphorylation increase positive charge
followed by chromatin condensation.13-01-2017

28. RNA MEDIATED SILENCING
• Involvement of sRNAs
Micro RNAs
Small interfering RNAs
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• RNA interference (RNAi)
is a biological process in
which RNA molecules inhibit
gene expression , typically by
causing the destruction of
specific mRNA molecules.
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29. EXPERIMENTS WITH EPIGENETICS
• HOW OUR LIFE STYLE CAN INFLUENCE ON
OUR PROGENY?
- Men who smoke before puberty tend to have sons
who can’t produce sperm, have higher body mass
indexes and shorter life expectancies.
- Smoking and over-eating can make the genes for
obesity over-express themselves and the genes for
longevity under-express themselves.
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31. YOU ARE WHAT YOUR GRANDMOTHER ATE.
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32. WHETHER EPIGENETIC MARKS
ARE INHERITED ?
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33. WHETHER WE CAN CONTROLE OUR DNA ?
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35. GOOD NEWS
• Scientists are learning to manipulate epigenetic
marks and are making drugs that will treat sickness
by turning off the bad genes and turning on the
good ones.
• Scientists are hoping to develop epigenetic drugs to
help people with diabetes, cancer, Alzheimer’s,
schizophrenia, autism, etc.
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36. IMPLICATIONS IN AGRICULTURE.
Vernalization and epigenetics:
 how plants remember winter
 One of the remarkable aspects of the promotion
of flowering by vernalization is that plants have
evolved the ability to measure a complete winter
season of cold and to ‘remember’ this prior cold
exposure in the spring.
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38. Transgene Silencing
• Transgenes do not express as expected
• Expression of transgenes are suppressed
in transgenic plants after they have grown for
one or more generation is called gene
silencing
• Because
• Stress induced transgene inactivation-
transgene that are integrated into genomic
regions which are subjected to epigenetic
modifications during stress treatment are
succeptible to environmentally indced
silensing
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39. Plant stress tolerance: –
Methylation pattern changes during stress helps
plants to tolerate stress
Genomic Imprinting:-
Parental genome equilibrium required for proper
seed development (2:1 maternal to paternal
genome for proper endosperm development
Epigenetic Variation
Soma clonal variation 39
OTHER IMPLIICATIONS
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40. Contributions to Science Work
and Society
• The new evidence for epigenetic inheritance has
had great implications for the study of evolution.
• It extends the span of evolutionary thinking and is
leading to ideas of heredity that include
development.
 And it also suggests that acquired traits can be
heritable, so Lamarck wasn’t completely wrong
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