Lesson 1 - Introduction Flashcards
“the greatest progressive minds of embryology have not looked for hypotheses; they have looked at embryos”
Jane Oppenheimer (1955)
merging of two sciences that are intricately intertwined in the development of the organisms
developmental biology
the two sciences that were merged to form developmental biology
- embryology
- genetics
what is the central paradox of life
how a single fertilized egg can five rise to a multicellular complex organism
study of the origin and development of an organism from a fertilized egg to the period resembling an adult form
embryology
importance of embryology
foundation of modern sciences
modern sciences
- anatomy
- pathology
- genetics
- evolution
- histology
- immunology
- physiology
- cellular biology
- ecology
where is the mechanisms on the development of organisms mainly responsible for
great diversity of animals
what does developmental biology deal with
- organogenesis
- postnatal development
different postnatal developments that were added to embryology to become developmental biology
- neoplastic growth
- metamorphosis
- regeneration
- tissue repair
abnormal proliferation of cells (tumors)
neoplastic growth
striking change of form or structure in an individual after hatching or birth
Metamorphosis
the regrowth of body parts from pieces of organism
regeneration
repair of tissue at levels of complexity ranging from the molecular to the organismal level
tissue repair
- genetic mechanisms involved in the development of an organism
- manifestation of traits coded in the genes
- genotype translated into phenotype
developmental genetics
two times bigger than ordinardy zebra
zebroid foal
Different fields of embryology
- descriptive embryology
- comparative embryology
- experimental embryology
- chemical embryology
- reproductive embryology
- teratology
accounts on the processes of development which transformed a single cell zygote to a multicellular organism
descriptive embryology
what question does descriptive embryology answer
what
- analysis of similarities and differences in the develpment of different vertebrate groups
- provides insight that ontogeny recapitulates phylogeny
comparative embryology
when did comparative embryology emerge
19th century
what does comparative embryollogy provide
valuable clues to taxonomic relationship among species by studying embryonic development
greatest interest in evolution, dominating factor in biology
driving force
what did comparative embryology lead to
- recognition of different moes of development of many species
- adoption of a number of species as model systems for experimental studies
stage in which embryos of different groups are virtually alike
stage 1
testing a hypothesis and manipulating the embryo by experiments
experimental embryology
an organ or tissue removed from one individual to be transplanted into another belonging to the same species
homotransplantation
refers to the process of grafting or transplanting organs or tissues between members of different species
Xenotransplantation
one of the pioneers of experimental biology
Wilhelm Roux
acquisition of detailed structural information on embryos
experimental embryology
cells that can develop into any cell type in an organism, including embryonic and extraembryonic tissues
Totipotent cells
- unspecialized cells that can differentiate into a limited number of specialized cell types
- found in specific tissues and are responsible for tissue repair and regeneration.
Multipotent stem cells
can only develop into all cell types within the body itself, not the extraembryonic tissues
pluripotent cell
when did Wilhelm Roux pioneer in the field of experimental embryology
1850-1924
what did Wilhelm Roux’s experiments provided proof for
- preformation or
- epigenesis doctrine
what term did Roux coin
developmental mechanics
preferred the term epigenetics
Waddington
development is brought about by a series of causal interaction between the various parts
epigenetics
what did Waddington remind
genetic factors are among the most important determinants of development
arose from the rapid growth of research related to problems of conception and contraception
reproductive biology
where does reproductive biology place a heavy emphasis on
- normal gametogenesis
- transport of gametes and fertilization
- endocrinology of reproduction
- early embryonic development
- implantation of the mammalian embryo
- chemical and physical events in development
- interacton of factors affecting development
- provided descriptive information about chemical and physiological events in the embryo
chemical embryology
when did chemical embryology rise
1930-1940
- study of birth defects
- deals with abnormalities and malformations in development due to genetic events and exogenous factors
teratology
genetic events in teratology
- mutations
- aneuploidy
- translocation
exogenous factors in teratology
- drugs
- radiation
- alcohol
- bacteria and viruses
condition in which the long bones of the limbs are either absent or severely deficient
phocomelia
where is phocomelia derived from
- phoco = seal
- melia = limb like a seals’ flipper
causes phocomelia
- genetic inheritance and/or mutations due to radiation
- oral intake of Thalidomide
allow childless couples to have children from their own genetic heritage
- in-vitro ferilization (IVF)
- embryo transfer (ET)
problems of IVF and ET
- obtaining fertile eggs from mother by laparoscopy - problem of ferility drugs
- surrogate mothers - refusal to give up baby
- frozen embryos
- manipulation of embryos - chimeras, cloning
- gene transfer
- diagnosis of genetic diseases
process of creating a genetically identical living being
cloning
first ever cloned animal
Dolly
who successfully cloned Dolly
researchers from Roslin Institute
Pioneers in Developmental Biology
- Aristotle
- Galen
- Anton van Leeuwenhoek and Hamm
- Reiner de Graaf
- Lazzaro Spallanzani
- Marcello Malpighi
- Karl Ernst von Baer
- Caspar Friedrich Wolff
- Matthias Schleiden and Theodor Schwann
- August Weissman
- Ernst Haeckel
- Hans Adolf Eduard Driesch
- Hans Spemann and Hilde Mangoid
- Wilhelm Johannsen
- Wilhelm Roux
- Salome Gluecksohn
- Conrad Hal Waddington
- posed the question on how the different parts of embryo were formed
- defined preformation and epigenesis
aristotle (384-322 BC)
what did aristotle define
- preformation
- epigenesis
a minature embryo already existed and got bigger
preformation
gradual formation of new structure (like knitting of net)
epigenesis
two schools of thought
- spermists
- ovists
the sperm contained the new individual in miniature and is merely nourished in the ovum
spermists
tiny human in the head of sperm
encasement concept “homunculus”
argued that the ovum contained a minute body which was stimulated to grow by the seminal fluid
ovists
he strengthened the ovists’ cause when he discovered that some of the eggs of insects can develop parthenogenetically
Charles Bonnet
- learned much about the strcture of relatively advanced fetuses
- Restriction: the minute dimenstions of early embryos prevented serious analysis
- Solution: development of microscope (17th century)
Galen (130-200 AD)
restriction in Galen’s time
minute dimensions of early embryos prevented serious analysis
solution of Galen’s restriction
development of microscope in 17th cen.
- first to see human sperms with a crude microscope
- from a drop of pond water, he saw bacteria, protozoans, and the sperm cells
- Anton van Leeuwenhoek
- Hamm
(1677)
what did Anton van Leeuwenhoek and Hamm use to see human sperms and other minute objects
crude microscopes
- founder of modern reproductive biology
- described the ovarian follicles
- first to describe the fallopian tubes
Reinier de Graaf (1672)
what did Reinier de Graaf describe
- ovarian follicles
- fallopian tubes
- demonstrated that in normal circumstancs, both female and male sex products are necessary for the initiation of development
- Italian priest, physiologist, and natural scientist
Lazzaro Spallanzani (1729-1799)
- accurately described the development of the chick in its egg
- published the first microscopic accound of chick development (1672)
- unconvinced of epigenesis because the unincubated egg had many structures
- italian embryologist
Marcello Malpighi (17th century)
what did Marcello Malpighi accurately describe
development of chick in its egg
when did Marcello Malpighi publish the first microscopic account of chick development
1672
why is Marcello Malpighi unconvinced of epigenesis
because the unincubated egg had many structures
- developed the science of comparative embryology
- existence of germ layers in embryos
- Russian zoologist
Karl Ernst von Baer (1792-1876)
what did Karl Ernst von Baer develop
developed comparative embryology
“The more general basic features of any animal group appear earlier in development than do the special features that are peculiar to different members of the group”
Von Baer’s Law
What is Von Baer’s Law
“The more general basic features of any animal group appear earlier in development than do the special features that are peculiar to different members of the group”
what did Karl Ernst von Baer propose
Germ layer theory
development of ectoderm, mesoderm, and endoderm
germ layer theory
what did Karl Ernst von Baer investigate
cleavage
what did Karl Ernst von Baer discover
- chick notochord
- mammalian egg
Three main points of Von Baer’s Law
- general features of a large group of animal appear earlier in development than do the specialized features of a smaller group
- demonstrated the existence of germ layers in embryos
- with the formulation of cell theory, the foundation of modern embryology was laid down and embryology as a sicence began
Von Baer’s Law:
- appear earlier in development than the specialized features of a smaller group
general features of large group
- proposed that embryonic development occurs through progressive remodeling and growth
- supported the theory of epigenesis
- German biologist
Caspar Friedrich Wolff (18th century)
- proposed the cell theory
- development must be via epigenesis
- the foundation of moderm embryology was laid down and embryology as a science began
- Matthias Schleiden
- Theodor Schwann
what does the Cell Theory state
- cells are basic unit of life
- cells arose only from pre-existing cells
- cells contain genetic information which is inherited by the offspring
- observed sea urchin’s egg fertilization and cleavage
- distinguished betwen soma and germ-cell line
August Weissmann (1880)
what did August Weissman distinguish
somatic cells from germ cells
vehicle for protecting and perpetuating germ plasm
somatic cells
- import for perpetuation of the species
- where offspring inherit their characteristics
germ cells
what did August Weissmann say about the zygotes
contains two nuclei derived from egg and sperm
what did the nuclei contain according to August Weissmann
factors that are asymmetrically distributed in the daughter cells
what predetermines the fate of each cell in the egg
factors it would receive during cleavage
what is the model of the egg receiving asymmetric factors called
mosaic
what are the major phases of the life cycle of a typical vertebrate
ADULT -> gametogenesis -> egg + sperm -> fertilization -> cleavage -> gastrulation -> organogenesis -> fetal growth -> hatching or birth -> juvenile -> ADULT -> senescence -> death
- developed the controversial recapitulation theory / biogenetic law
- claims that an individual organism’s biological development, or ontogeny, parallels and summarizes its species’ entire evolutionary development or phylogeny
Ernst Haeckel (1868)
what did Ernst Haeckel develop
Recapitulation theory / Biogenetic Law
what does the Recapitulation theory / Biogenetic Law state
ontogeny recapitulates phylogeny
- demonstrated that it was possible to remove large pieces from eggs, such as shuffling the blastomeres at will or taking some away and thus interfere in many ways, yet not affect the resulting embryo
- any single monad in the original egg cell was capable of forming any part of the completed embryo
- leads to the terms totipotent and puripotent cell
Hans Adolf Eduard Driesch (1867-1941)
what did Hans Adolf Eduard Driesch demonstrate
it was possible to remove large pieces from eggs, such as shuffling the blastomeres at will or taking some away and thus interfere in many ways, yet not affect the resulting embryo
can generate all cells in an organism
totipotent cell
totipotent
total + potential
can generate certain cells in an organism
pluripotent cell
ability of embryo to develop normally even if some cells are removed or rearranged
regulative development
what is Roux’s earlier finding that was contradicted by Driesch’s experiment
if one of the cells of a two-cell from an embryo is damaged, the remaining cell develops into a half embryo
- did the transplantation experiment
- led to the discovery of organizer or evocator
- Hans Spemann
- Hilde Mangold
(1924)
what is the transplantation experiment about
- dorsal lip of blastopore grafter from an unpigmented species of newt to blastocoel roof of pigmente species
- secondary embryo is induced
(partial secondary embryo can be induced by grafting a small region of a new embryo onto a new site on another embryo)
- responsible for controlling the organization of a complete embryonic body
- blocks the action of BMP-4 by secreting molecules of the proteins chordin and noggin
- ectodermal cells are allowed to follow their default pathway, which is to become nerve tissue of the brain and spinal cord
Spemann-Mangold organizer
- distinguished between genotype and phenotype
- Danish biologist
Wilhelm Johannsen (1857-1957)
genetic information or endowment of an organism acquired from its parents
genotype
visible appearance, internal structure or biochemistry at any stage of development
phenotype
relationship between genotype and phenotype
how the genetic endowment is “translated/expressed” during development to give rise to a functioning organism
- did the ablation experiment or embryonic extirpation
- development of frog is based on Mosaic mechanism
- German embryologist
Wilhelm Roux in late 1896
took 2- and 4-cell from embryos and destroyed some of the cells of each embryo with a hot needle to determine whether the remaining cell will give rise to only have an embryo or could restore the deficiency during subsequent development
Ablation Experiment of Embryonic Extirpation
Roux’s experiment was done to investigate whose theory?
Weismann’s theory
- worked on mutant genes of mouse and Drosophila
- integrated genetics and embryology = developmental genetics
- Salome Gluecksohn Waelsch
- Conrad Hal Waddington
(1930)
determine the properties of a cell during development
genes econde proteins
- development is brought about by a series of causal interactions between the various parts
- reminds one that genetic factors are among the most important determinants of development
epigenetics
