Chapter 47: Animal Development

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Chapter 47 Animal Development

1. What exactly happens when sperm meets egg?

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Figure 47.3 The acrosomal and cortical reactions
during sea urchin fertilization
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• Contact acrosome releases hydrolytic enzymes
• Acrosomal rxn enzymes digest jelly coat while
  actin extends
• - acrosomal process attaches to sperm binding
  receptors
• Membrane fusion (sperm egg) causes
  depolarization as Ca2 released
• - aka fast block to polyspermy
• - aka activation of the egg begins
• Sperm nucleus enters egg
• Cortical rxn cortical granules from egg fuse
  with plasma membrane
• Forms fertilization envelope aka slow block to
  polyspermy
• What happens with activation of the egg?
• Ca2 released from ER
• ? Cellular respiration ? protein synthesis
  (translation)

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Figure 47.4 What is the effect of sperm binding
on Ca2 distribution in the egg?
500 ?m
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Figure 47.5 Timeline for the fertilization of sea
urchin eggs
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• What happens with activation of the egg?
• What happens in mammals?

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Figure 47.6 Early events of fertilization in
mammals
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• What happens with activation of the egg?
• What happens in mammals?
• Contact sperm migrates through follicle cells
  binds to zona pellucida
• Acrosomal rxn acrosome releases hydrolytic
  enzymes digesting ZP
• Sperm bind to sperm receptors on 2 oocyte
  membranes fuse
• Sperm nucleus enters egg
• Cortical reaction hardens ZP as a block to
  polyspermy
• What happens with during cleavage?
• Cell division w/o cytokinesis
• Creates blastomeres
• Axes formed at first cleavage in amphibians

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Figure 47.8 The body axes and their establishment
in an amphibian
Anterior
Body axes. The three axes of the fully developed
embryo, the tadpole, are shown above.
(a)
Right
Dorsal
Ventral
Left
Posterior
Animal hemisphere
Animal pole
Point of sperm entry
The polarity of the egg determines the
anterior-posterior axis before fertilization.
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Vegetal hemisphere
Vegetal pole
Point of sperm entry
At fertilization, the pigmented cortex slides
over the underlying cytoplasm toward the point of
sperm entry. This rotation (red arrow) exposes a
region of lighter-colored cytoplasm, the gray
crescent, which is a marker of the dorsal side.
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Future dorsal side of tadpole
Gray crescent
First cleavage
The first cleavage division bisects the gray
crescent. Once the anterior- posterior and
dorsal-ventral axes are defined, so is the
left-right axis.
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(b)
Establishing the axes. The polarity of the egg
and cortical rotation are critical in setting up
the body axes.
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Figure 47.9 Cleavage in a frog embryo
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• What happens with activation of the egg?
• What happens in mammals?
• What happens with during cleavage?
• What is gastrulation?
• Movement of blastula cells into the blastopore
  creating 2 cell (germ) layers
• Ectoderm outer layer
• Endoderm inner layer
• Mesoderm forms in between

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Figure 47.12 Gastrulation in a frog embryo
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• What happens with activation of the egg?
• What happens in mammals?
• What happens with during cleavage?
• What is gastrulation?
• What is organogenesis?
• Creation of organs
• Involves folds, splits clustering of cells
• 1st organs are neural tube notocord

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Chapter 47 Animal Development
Students Correlations available now sorry for
the delay ? Learning Log later today AP
checks?? March 9 deadline Has anyone not taken
the Biology EOC? Transfers, movers,
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Figure 47.14 Early organogenesis in a frog embryo
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Figure 47.16 Adult derivatives of the three
embryonic germ layers in vertebrates
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• What happens with activation of the egg?
• What happens in mammals?
• What happens with during cleavage?
• What is gastrulation?
• What is organogenesis?
• What are the 4 extra-embryonic membranes in the
  amniotic egg?
• Amnion
• Allantois
• Chorion
• Yolk sac

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Figure 47.17 Extraembryonic membranes in birds
and other reptiles
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• What happens with activation of the egg?
• What happens in mammals?
• What happens with during cleavage?
• What is gastrulation?
• What is organogenesis?
• What are the 4 extra-embryonic membranes in the
  amniotic egg?
• How does mammalian development occur?
• Slow cleavage
• 1st division 36 hrs
• 2nd 60 hrs
• 3rd 72 hrs

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Figure 47.18 Four stages in early embryonic
development of a human
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• What happens with activation of the egg?
• What happens in mammals?
• What happens with during cleavage?
• What is gastrulation?
• What is organogenesis?
• What are the 4 extra-embryonic membranes in the
  amniotic egg?
• How does mammalian development occur?
• What three things influence cell fate?
• Cytoplasmic determinants mRNA proteins in egg
  cytoplasm
• Induction cellular peer pressure
• Cleavage pattern divides cytoplasmic
  determinants

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Figure 21.11 Sources of developmental information
for the early embryo
Nucleus
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Figure 21.11b
Cellular peer pressure
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Figure 47.24 How does distribution of the gray
crescent at the first cleavage affect the potency
of the two daughter cells?
Left (control) Fertilized salamander eggs were
allowed to divide normally, resulting in the gray
crescent being evenly divided between the
two blastomeres.
Right (experimental) Fertilized eggs
were constricted by a thread so that the first
cleavage plane restricted the gray crescent to
one blastomere.
Gray crescent
Gray crescent
The two blastomeres were then separated
and allowed to develop.
Belly piece
Normal
Normal
Blastomeres that
receive half or all of the gray crescent develop
into normal embryos, but a blastomere that
receives none of the gray crescent gives rise to
an abnormal embryo without dorsal structures.
Spemann called it a belly piece.
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Figure 47.25 Can the dorsal lip of the blastopore
induce cells in another part of the amphibian
embryo to change their developmental fate?
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• What happens with activation of the egg?
• What happens in mammals?
• What happens with during cleavage?
• What is gastrulation?
• What is organogenesis?
• What are the 4 extra-embryonic membranes in the
  amniotic egg?
• How does mammalian development occur?
• What three things influence cell fate?
• How are organisms formed from the fertilized
  egg?
• Cell division/cleavage
• Morphogenesis process of giving shape to an
  organism
• Cell differentiation process by which cells
  become specialized

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Figure 21.4 Some key stages of development in
animals and plants
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• What happens with activation of the egg?
• What happens in mammals?
• What happens with during cleavage?
• What is gastrulation?
• What is organogenesis?
• What are the 4 extra-embryonic membranes in the
  amniotic egg?
• How does mammalian development occur?
• What three things influence cell fate?
• How are organisms formed from the fertilized
  egg?
• Can cells de-differentiate?
• Plant cuttings
• Animal cells????

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Figure 21.6 Can the nucleus from a differentiated
animal cell direct development of an organism?
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• What happens with activation of the egg?
• What happens in mammals?
• What happens with during cleavage?
• What is gastrulation?
• What is organogenesis?
• What are the 4 extra-embryonic membranes in the
  amniotic egg?
• How does mammalian development occur?
• What three things influence cell fate?
• How are organisms formed from the fertilized
  egg?
• Can cells de-differentiate?
• How was Dolly cloned?
• - Nuclear transplantation

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Fig. 21.7 Reproductive Cloning of a Mammal by
Nuclear Transplantation
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Figure 21.9 Working with stem cells
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• What happens with activation of the egg?
• What happens in mammals?
• What happens with during cleavage?
• What is gastrulation?
• What is organogenesis?
• What are the 4 extra-embryonic membranes in the
  amniotic egg?
• How does mammalian development occur?
• What three things influence cell fate?
• How are organisms formed from the fertilized
  egg?
• Can cells de-differentiate?
• How was Dolly cloned?
• When is a cell determined (fated)?
• - Muscle cells MyoD transcription factor
  turns on all muscle genes

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Figure 21.10 Determination and differentiation of
muscle cells
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Figure 21.10 Determination and differentiation of
muscle cells
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Figure 21.10 Determination and differentiation of
muscle cells
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• What happens with activation of the egg?
• What happens in mammals?
• What happens with during cleavage?
• What is gastrulation?
• What is organogenesis?
• What are the 4 extra-embryonic membranes in the
  amniotic egg?
• How does mammalian development occur?
• What three things influence cell fate?
• How are organisms formed from the fertilized
  egg?
• Can cells de-differentiate?
• How was Dolly cloned?
• When is a cell determined (fated)?
• What is apoptosis?
• - Programmed cell death cell suicide

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Figure 21.18 Molecular basis of apoptosis in C.
elegans
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Chapter 47 Animal Development

• What exactly happens when sperm meets egg?
• What happens with activation of the egg?
• What happens in mammals?
• What happens with during cleavage?
• What is gastrulation?
• What is organogenesis?
• What are the 4 extra-embryonic membranes in the
  amniotic egg?
• How does mammalian development occur?
• What three things influence cell fate?
• How are organisms formed from the fertilized
  egg?
• Can cells de-differentiate?
• How was Dolly cloned?
• When is a cell determined (fated)?
• What is apoptosis?
• What are some model organisms for studying
  development?

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Figure 21.2 Model Organisms for Genetic Studies
of Development
Drosophila - small, easy cheap to culture - 2
week generation time - 4 chromosomes - LARGE
literature of info
C elegans - easy to culture - transparent body
with few cell types - zygote to mature adult in
3 days
0.25 mm
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Mouse - vertebrate - LARGE literature
- transgenics knock-outs