The Origin of Developmental Biology
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Transcript of The Origin of Developmental Biology
The Origin of Developmental Biology
BYZeinab SalahDalia Ahmed
The Origin of Developmental Biology
BYZeinab SalahDalia Ahmed
Definition
• Developmental biology is the branch of life
science, which deals with the study of the process
by which organisms grow and develop and which
the genes in the fertilized egg control cell behavior
in the embryo and so determine its pattern, its form,
and much of its behavior.
• It is an integration of embryology ( the study of embryonic
development) with cytology (the study of cellular structure
and function) and later with genetics (the study of
inheritance).
• Modern developmental biology studies the genetic control
of cell growth, differentiation and "morphogenesis," which
is the process that gives rise to tissues, organs and
anatomy.
Historical background
Hippocrates in 5th century BC ; He tried to explain development in terms of the
principles of heat, wetness, and solidification.
Aristotle; Established ‘embryology’ as an independent field .
Defined epigenesis and preformation.
.
• Preformation theory suggests that all structures
exist from the very beginning, they just get larger.
• Epigenesis (~upon formation) is a theory of
development that states that new structures arise by
progressing through a number of different stages.
• Marcello Malpighi in 17th century :• Italian embryologist.
• He provided a remarkably accurate description of the
development of the chick embryo.
• He argued that at the very early stage the parts were so
small that they can not observed even by his best
microscope.
• Mathais Schleiden and Theodor Schwann
(1838-39) ;• Developed the Cell Theory.
• This theory is one of the foundations of biology. The
theory says that new cells are formed from other existing
cells, and that the cell is a fundamental unit of structure,
function and organization in all living organisms.
• August Weismann (1834 – 1914);
• German evolutionary biologist.
• Weismann's theory of inheritance
• Proposed that the sperm and egg provided equal
chromosomal contributions, both quantitatively and
qualitatively, to the new organism. Moreover, he postulated
that the chromosomes carried the inherited potentials of
this new organism and hypothesized that only the germ
cells contained all the inherited determinants.
•Mosaic development depends upon specific determinants in the one-celled zygote that are not divided equally between the daughter cells (asymmetric division).
• Wilhelm Roux (1888) ;• German embryologist.
• He support weismann’s theory by experiments in frog
embryos, he destroyed one of the two cells with hot
needle and then result into well –formed half larva.
Early evidence for mosaic development
• He concluded that the frog embryo was a mosaic of self-
differentiating parts and that it was likely that each cell
received a specific set of determinants and differentiated
accordingly.
• Hans Driesch( 1892);• Demonstrate regulative development which depends
upon interactions between 'parts' of the developing
embryo can result in causing different tissues to form
(even if parts of the original embryo are removed).
Driesch destroyed one cell of a sea urchin embryo at the
two cell stage and a normal appearing but smaller sea
urchin larvae resulted.
Sea Urchin Embryos show regulative Development
• So is development mosaic or
regulative?
• A. It is a combination of both
• Hans Spemann and Hilde Mangold;• Discovery of primary Embryonic Induction.
• Induction is a type of regulatory development.
• They proved the importance of induction and other cell-cell
interactions in development by transplant experiment in
amphibian embryos.
Spemann and Mangold transplanted dorsal lip of the blastopore to a different blastula and a new main body axis developed.
• Gregor Mendel's;• In 1900, the significance of Gregor Mendel's
work on heredity was finally appreciated.
• Mendel was the first scientist to develop a
method for predicting the outcome of
inheritance patterns.
• He is the father of modern genetics for his
study of the inheritance of traits in pea plants.
• Mendel showed that the inheritance of traits
follows particular laws, which were later
named after him.
Theodor Boveri;
German biologist.
Had major support for the chromosomal hypothesis of inheritance.
One of the biologists who felt that the nucleus contained the instructions
for development who in a paper published in 1902 demonstrated that
normal development is dependent upon the normal combination of
chromosomes.
• .
• Thomas Hunt Morgan • American geneticist and embryologist.
• Noted in 1926 that the only way to get from genotype to
phenotype is through developmental processes.
• Morgan redefined genetics as the science studying the
transmission of traits, as opposed to embryology, the
science studying the expression of traits.
He able to combine genetics with developmental biology and
create the discipline of developmental genetics.
Morgan had shown that nuclear chromosomes are
responsible for the development of inherited characters.
The final proof of the chromosome theory of inheritance
resulted from research using the fruit fly, Drosophila
melanogaster that was conducted in Thomas Hunt Morgan's
laboratory at Columbia University.
Animal Development
Animal Development
• Summarize the basic steps in animal develop
starting gametogenesis and ending with death.
• GAMETOGENESIS
– Specialization of ovum and sperm
• FERTILIZATION
– Block of polyspermy
• CLEAVAGE
– Cell division without an increase in total volume
• MORULA
– Solid mass of cells
• BLASTULATION
– Hollow mass of cells
5 Processes of Development
1. Cleavage Division:
No increase in cell mass
2. Pattern Formation:
A/P(anterior head/ posterior tail) and D/V axes(Dorsal upper or
back/Ventral lower or front): Coordinate system
3. Morphogenesis:
take 3D form.
.
4. Cell Differentiation:
cells become structurally and functionally different.
5. Growth:
cell multiplication, increase in cell size, deposit
extracellular material (bone, shell) growth can be
morphogenetic
• Developmental model organisms
• Vertebrates
– Zebrafish Danio rerio
– Frog Xenopus laevis, Xenopus tropicalis
– Chicken Gallus gallus
– Mouse Mus musculus
• Invertebrates
– Roundworm Caenorhabditis elegans
– Fruit fly Drosophila melanogaster
The developmental-genetic toolkit
• Consists of genes whose products control the
development of a multicellular organism.
• The majority of toolkit genes are components of
signaling pathways, and encode for the production
of transcription factors, cell adhesion proteins, cell
surface receptor proteins, and secreted
morphogens.
• The most important toolkit genes are those of the Hox gene
cluster.
• Mutations in any one of these genes can lead to the growth of
extra, typically non-functional body parts in invertebrates, for
example aristapedia complex in Drosophila, this mutation is known
as Antennapedia.
• The genes that regulate development are best understood in two
species, the mouse
• and the fruitfly
HOMOLOGOUS HOX SEQUENCES:EXPRESSION
HOMOLOGOUS HOX GENES: DERIVATION
MUTATIONS INREGULATORY GENES CAN GIVE THE PROTEINS NEWPROPERTIES: UBXACQUIRES THE ABILITY to REPRESS DISTAL-LESS in the INSECT CLADE
Evolutionary developmental biology
• “Evolution is a change in the genetic composition of populations.
• The study of the mechanisms of evolution falls within the province
of population genetics.” Theodosius Dobzhansky. 1951
Evolutionary developmental biology
• The emergence of new phenotypes is made
possible by changes in development. The regulatory
genes that have long been thought to control the
generation of novel structures are now being
discovered
• Evolutionary developmental biology, now often
known as “evo-devo,” is the study of the relation
between evolution and development. The relation
between evolution and development has been the
subject of research for many years, However, the
subject has been transformed in recent years as the
genes that control development have begun to be
identified.
The Modern Era
• The Impact of Molecular and Cellular Biology
• The molecular biology revolution in the middle of the
Twentieth Century provided the means to study the
role of genes in development that Wilson and his
contemporaries lacked. The key technological
advance for the study of gene control of development
was the ability to isolate and clone genes.
• Much of the current research in developmental
biology involves attempts to understand the cellular
and intercellular events that signal the nucleus to
express genes or initiate a sequence of gene
expression.
There are two powerful techniques allow investigators
to test directly the roles of specific genes during
development:-
• Introduce cloned genes into embryos and assess
their effects on development.
• Eliminate or "knock out" specific genes and
determine the effects on development.
THANK YOU
References
• Developmental biology 6th edition. Gilbert