Deepakshi dev bio presentation_124928.pdf

Biochemistry

1. E
XPERIMENTALD
EVELOPMENTAL
B
IOLOGY
(
M
ODEL
O
RGANISMS
)
Presented by DeepakshiGayen
RegNo: 23LBMS26
MSc Biochemistry

2. Experimental Developmental
Biology:
Experimental developmental
biology involves controlled
experiments to investigate the
processes by which organisms
develop.
Research goals to understand:

Cellular differentiation (how
cells become specialized).

Morphogenesis(how tissues and
organs form).

Ethics and Practicality: Easier
than working directly with
humans.

Genetic Homology: Many
organisms share genes with
humans.
Criteria for Selecting Model
Organisms:

Practical Features: Short
generation times, small size, and
high reproductive rate.

Genetic Tractability: Genetic
tools (e.g., CRISPR/Cas9,
organs form).

Organogenesis(formation of
functional organs).
Model organisms:
Model organisms are non-human
speciesthat are studied to
understand biological processes
and how they relate to other
organisms.
Importance of Model Organisms :

Reproducibility: Same species
can be used worldwide.

Genetic Tractability: Genetic
tools (e.g., CRISPR/Cas9,
knockouts).

Ease of Observation: Ability to
visualize development (e.g.,
transparent embryos).

Conservation of Pathways:
Similar developmental pathways
(e.g., Hoxgenes, signaling
cascades) between model
organisms and humans.

3. Why Drosophila?

One of the first genetically tractable
organisms used in developmental
research (T.H. Morgan, early1900s).

Short life cycle (10 days from egg to
adult).

Four pairs of chromosomes

14000 Genes, sequenced genome
and 2/3of human disease genes have
Discoveries & Future Aspects:

Discovery of homeotic(Hox) genes
Control the body plan of an organism.

Study of pattern formation:
Establishment of anterior-posterior and
dorsal-ventral axes.

Discovery of maternal effect genes
like bicoid: Control early patterning
of embryos.
Drosophila melanogaster(Fruit Fly)
and 2/3of human disease genes have
fly homologues.

Simple care requirements, cheap, and
robust genetic tools.
of embryos.

Insituhybridizationofwhole
embryocanreveal patternsofgene
expressionduringdevelopment

Polytenechromosome present in
salivary gland canbeusedtodetermine
binding siteoflabeledproteins.
Chromosomalrearrangmentsand
deletionscanbevisualized.

4. Nobel Prize Contributions:
1995: Edward Lewis, ChristianeNüsslein-Volhard, and Eric Wieschausfor
discovering genes that control embryonic development
Conservationofpatterningbetween fliesandmammals
anterior
posterior
HoxA
(Hox1)
parasegments
rhombomores
(Hox1)
HoxB
(Hox2)
E
E
HoxC
-------1
(Hox3)
HoxD
(Hox4)
rhombomores
12345678
VERTEBRATE

5. Why C. elegans?

Simple body plan, transparent body,
and invariant cell lineage.

Wormsareusuallykeptonpetriplates
andfedE.coli.

959 somatic cell, all visible under
microscope. 131 cells undergo
programmed cell death.

Genome contains 19000 fully
sequenced genes
Discoveries & Future Aspects:

Apoptosis:Mechanisms of programmed
cell death elucidated.

RNA interference (RNAi): Discovery
of gene silencing mechanisms by
Andrew Fire and Craig Mello (Nobel
Prize,2006).

Gene function studies have become
relatively simple with the recent
discovery of RNAi.
Caenorhabditiselegans(Nematode)
sequenced genes

70% of human geneshave worm
homologues.

Only302neurons, making it ideal for
neurodevelopmentalstudies.
discovery of RNAi.

Full connectome(complete map of
neural connections) mapped.
Key Genetic Techniques:
Gene knockdowns using RNAi,
CRISPR/Cas9 for gene editing.
Applications:
Aging studies, neurobiology, innate
immunity.

6. Why Zebrafish?

Vertebrate modelwith clear
homologsto human genes.

Transparent embryos allow real-
time observation of organogenesis.

Rapid development: Major organs
form within24-48hours post-
fertilization.
Discoveries & Future Aspects:

Role of Notch signaling in
segmentation.

Insights into heart development and
regeneration (zebrafishcan
regenerate heart tissue).

Genetic basis of organ development:
Kidney, liver, and pancreas.
Daniorerio(Zebrafish)
Applications:
Cardiovascular biology, cancer
biology, drug screening.

7. Why Xenopus?

Large, easily manipulated embryos
ideal for studying early embryogenesis.

External development allows
observation and manipulation of the
developing embryo.

Largesizeallowsstudyof
movementofcells withinXenopus
embryos
Germlayersandstructural
Discoveries & Future Aspects:

Spemann-Mangoldorganizer : First
discovered in amphibians, critical for
patterning the dorsal-ventral axis.

Studies of cell fate determination:
Induction and differentiation.

Discovery of key signaling
pathways: Wnt, BMP, and TGF-β.
Experimental Techniques:
Xenopuslaevis(African Clawed Frog)

Germlayersandstructural
characteristicsareeasily observed.
Experimental Techniques:

Microinjectionof mRNA, morpholino
oligonucleotides, and CRISPR/Cas9.

Fate mapping using dye-labeling
techniques.
DiffuseintemA.I
cytoplasm
Anlmalpole
Heavyyolk
plot.Jets
Vtg,talpole

8. TheEmbryonicSignalingCenter: Spemann'sOrganizer

ClassicexperimentfirstperformedbySpemann andMangoldin1924

Grafteddorsallipofanembryoontoasecond embryo

Gastrulationinitiatedatbothsites

Secondwholesetofbodystructuresformed
Double
embryo
develops with
nearly all its
tissues of host
origin
Dorsal lip of
blastopore
grafted
CellfatestudiesinXenopus:Noggin

Nogginexpressionpermits cellstobecome brainand nervoussystem
tissue

NoNogginexpression resultsintissuebecoming skin,bone
origin

9. Why Mouse?

Mammalian model organism , with
high similarity to humans (~99% of
genes shared).

Life cycle 9 weeks

Genome sequenced

Genetic manipulation well
developed.
Discoveries & Future Aspects:

Gene knockout technology
pioneered here: Used to study the
function of specific genes.

Martin Evans and Matthew established
embryonic stem cell technology in
mouse embryo. (Nobel Prize,2007)

Models of human diseases: Cancer,
diabetes, neurological disorders.
Understanding of immune system
Musmusculus (Mouse)

Understanding of immune system
development.
Applications:

Mouse embryonic stem cell lines for
creating transgenic and knockout
mice.

Models for human development, genetic
diseases, and therapeutic testing.

10. Why Arabidopsis?

Model plant for studying genetics,
development, and physiology.

Small genome (~125Mb), fully
sequenced

Short generation time (6 weeks).
Discoveries & Future Aspects:

Floral development: ABC model of
flower development.

Studies of photomorphogenesis (how
plants respond to light).

Hormonal control of growth:
Auxins, cytokinins, and gibberellins.
Arabidopsis thaliana (ThaleCress)
Auxins, cytokinins, and gibberellins.
Applications:
Insights into crop improvement,
stress resistance, and plant-
pathogen interactions.

11. Why Sea Urchin?

Pioneered understanding of
fertilization and early cleavage
stages.

Transparent embryos and large size
made them ideal for early embryological
studies.
Key Contributions:

Role of calcium waves in fertilization.

Studies on developmental axes and
early cleavage patterns.

Model for studying gene regulatory
networks during development.Experimental Techniques:
In vitro fertilization, microinjection, live
imaging of calcium dynamics.
Sea Urchin
imaging of calcium dynamics.
Applications:
Insights into activation, and cell
division, embryogenesis, early
zygotic gene