Download Dev Biol L1

Developmental Zoology
(ZOO 228.1.0)
Dr. Dinithi Peiris
Dept. of Zoology
University of SJP
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Developmental Zoology
Unit Type
No: of Lecture Hours
Instructor
Attendance
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Course Description
How does a complex, multicellular organism
arise from a single cell?
What is known about the mechanisms that
accomplish this feat?
: Compulsory Course
: 15 hrs
: Dr Dinithi Peiris
: 80% attendance
This course aims to provide a broad look at
development integrating. We will explore the
basic body plan of the embryo and how
organs are formed, with special emphasis on
vertebrate models. Embryonic and Adult Stem
Cells will also be covered
Prerequisite- Zoo 123.1.0 - Cytology
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Intended Learning Outcomes
Intended Learning Outcomes
Upon successful completion of this course
students should be able to
 Describe process of gametogenesis,
fertilization, implantation
Upon successful completion of this course
students should be able to
 Describe the regulatory mechanisms of
morphogenesis in early animal embryos.
 Understand
the basis of development of
animal body, and molecular mechanisms
regulating developmental processes.
phenomena relating animal
development including axis formation, cell
differentiation, and morphogenesis.
 Understand
various aspects of tissue
interactions observed in organs in later
stages of embryonic development
 Describe
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Assessment
References
Assignment 1: Tutorial (10%)
Must complete the assignment 1 to sit for
the final theory exam.
• • Methods of Assessment:
1. Mid term exam 2. Tutorial
3. One hour final exam Slack J. (2001) – Essential developmental
biology. Blackwell publications. USA.
(20%)
(10%)
(70%)
• Gilbert
S.
(2002)
biology,
9th
Edition.
Online
–
Developmental
resources
-http://
www.nature.com/milestones/development/
milestones/index.html 7
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What is Animal Development
What is Animal Development
 Developmental
Biology is the study of a
PROCESS whereby a single cell divides
and selectively activates expression of
genes to produce a complex organism
composed of many cell types.
 The
process by which a fertilized egg
transforms itself into a complex organism is
one of the most exciting and complex
mysteries in the field of biology!
 How
does it happen?? Each of us sitting in
this room developed from a single egg!
 Ex
ovo omnia = all from the egg. 1651
William Harvey proposed that all animals
originate from eggs•
 What are the types of PROCESSES
required?
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What is Animal Development
What is Animal Development
• During development single cell zygote give rise
to different cells with different function.
• Cells of similar types organized into tissues,
tissues into organs, organs into organ systems,
& organ systems into whole organism.
• Hence, embryonic development must give rise,
higher-level structures arranged in a particular
way in three dimensions
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• There is clearly something very special about a
fertilized egg cell.
• The genes in the genome are the driving force
behind development and they are also the
basis of the differences between organisms.
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What is Animal Development
• Question?
• How a single cell and end up with a complex
multicellular organism, with hundreds of
different cell types, all formed at the correct
time and in the correct place to build a
functioning body and perform all the
individual functions of life.
What is Animal Development
 A
central idea of development that we will
talk about many times the rest of the
semester is DIFFERENTIATION:
 All
cells have the same DNA, but different
cells express different genes. This is called
DIFFERENTIATION.
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What is Animal Development
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Animal Development
 This
PROCESS is studied using TOOLS,
many of which you have already heard
about:
– a) Cell Biology
– b) Genetics – c) Molecular Biology -
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1. The body is made of millions to billions of cells.
d) Each cell has a specialized task, e.g. muscle
cell, nerve cell, etc.
e) To carry out these specialized tasks, each cell
has special machinery
i. Nerve cell has machinery for
transmitting electrical and chemical signals
ii. blood cell has machinery to transport oxygen
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Basics?
Basics?
2. Cellular machinery is largely made up of proteins
Proteins are long chains of amino acids. Each
protein molecule has evolved to carry out a particular
task. E.g:
i. Hemoglobin in the blood binds to & carries
oxygen
ii Actin forms filaments that make up the
cytoskeleton
iii Ribosomal proteins help make up the
ribosome, the cell's protein factory
iv. Insulin is secreted by cells of the pancreas &
serves as a signal to other cells.
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3. Because of their different tasks,
different cells contain different
proteins:
While some proteins are found
in all cells (actin), others are
made only in specialized cells
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Basics?
Developmental Mechanisms
Differentiation mechanism:
4. Proteins are made up of chains or
sequences of amino acids, and these
amino acids are "encoded" in the
cell's DNA
a.
b.
Mosaic Development
DNA is organized in large segments known
as chromosomes
 1 gene encodes = 1protein
  c. Thus there is a myoglobin gene, an actin
gene, an insulin gene etc..
d.
Mutations in single genes result in ?
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Cells acquire fixed identity
No influence from neighboring cells
Isolated cells develop in to particular part of
the body
Autonomous Specification
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Developmental Mechanisms
Developmental Mechanisms
Wilhelm Roux's experiment in 1888
Hans Driesch's experiment in 1892
Regulative Development
 Sea urchin cells developed in to separate
parts.
 Most organisms combine information &
develop as a combination of Mosaic &
Regulative process.
 Cells are flexible
 Adjust according to neighboring cells & envt.
 When isolated, each cell can develop in to
an entire organism.
Conditional Specification
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Developmental Mechanisms
Developmental Mechanisms
Another way to state the basic question is
of Development is: How do cells know
which genes to activate as they go
through development?
What are the two sources of information cells?
 Different
 Two
cells activate different genes
sources of information cells
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1. Information from your mother
2. Information from your neighbors or
environment.
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Developmental Mechanisms
Developmental Mechanisms
Information from your mother
 Information from your neighbors or environment.
E.g .Gene expression patterns, or
Segregation of "determinants
• I. Informational molecules (e.g. protein
or mRNA).
 E.g. Cell-cell interactions. Communication can be
local, via direct cell-cell contacts, or global, via
diffusible molecules .
I. Maintain neighbors in quo.
II. incite neighbors to novel behaviors
ii. Inherited patterns of gene expression.
Iii. Information can be passed on uniformly,
or can be segregated to one of the progeny
cells.
III. The differences can then be transmitted to
cellular offspring
IV. Even unicellular organisms communicate!
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Developmental Mechanisms
Signaling Systems
E.g. of simple cell-cell communication
• Development depend on effects of one group of
cells on another.
 This is exerted by embryonic induction –
secrete inducing factors
 7 molecular families of inducing factors –
growth factors, cytokines or hormones
 Binding results in induction of signal
transduction pathway
 Leads to activation or suppression of certain
genes
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Yeast sex:
Haploid cells have 2 mating types; “a” or
“alpha”
•  Single-celled slime mold
Amoeboid type cells living on forest floor
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Signal Transduction
  Inducing Factor Families
Retinoic acid can diffuse across the plasma
membrane.
 Present in both vertebrates & invertebrates
1. Transforming growth factor β super family
(TGF β).
2. Fibroblast growth factor family (FGFs).
3. Epidermal growth factor (EGF)
4. Hedgehog family
5. Wnt family
Protein inducing factors cannot diffuse
across the membrane –
 G-protein linked receptors
 Ion channel receptors
 Tyrosine kinase (main receptors)
 Activation of receptors activates a cascade
and move to nucleus to activate target genes
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Developmental Mechanisms
PBL
Amber just returned from New York and, she had felt
sick the whole time, and the flu-like feeling still hadn't
subsided.
Question:
What are three broad inter-related
processes are involved in building an
organism
She was a little concerned, but attributed it mostly to
nerves and lack of sleep.
That night as she lay in bed reading, it felt like a
gong was going off in her head. Maybe she was on
edge over the recent break-up with her boy
Answer:
1. Cell division
2. Cell differentiation
3. Morphogenesis
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She went to sleep that night trying to ignore the
unfamiliar pains and feelings that were consuming her.
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