Molecular and Organismal
Development
Chapter 21: pp 411-429
Chapter 47: pp 992-1008
Topics in Development
• 1. totipotency: development depends on selective expression of
the whole genome present in every cell.
• 2. blastula to gastrula: comparative analysis yields insights into
the general nature of development
• 3. the three fundamental processes:
– cell division (differential rates of division are critical,
programmed cell death is significant)
– cell differentiation (changes in integration and shape are
critical; targeting cells with signals is a critical part of the
process)
– morphogenesis of tissues and organs (includes defining the
individual’s polarities, dividing the organism into segments,
and – in animals -- migration of cells in tissue origin)
Figure 21.2 Some key stages of development in animals and plants
Figure 21.5 Test-tube cloning of carrots
Figure 21.8 Working with stem cells
Topics in Development
• 1. totipotency: development depends on selective expression of
the whole genome present in every cell.
• 2. blastula to gastrula: comparative analysis yields insights into
the general nature of development
• 3. the three fundamental processes:
– cell division (differential rates of division are critical,
programmed cell death is significant)
– cell differentiation (changes in integration and shape are
critical; targeting cells with signals is a critical part of the
process)
– morphogenesis of tissues and organs (includes defining the
individual’s polarities, dividing the organism into segments,
and – in animals -- migration of cells in tissue origin)
Figure 47.6 Cleavage in an echinoderm (sea urchin) embryo
Figure 47.9 Sea urchin gastrulation (Layer 3)
Figure 47.8x Cleavage in a frog embryo
Figure 47.8d Cross section of a frog blastula
Figure 47.10 Gastrulation in a frog embryo
Figure 47.12
Gastrulation in a
frog embryo
Figure 47.12 Cleavage, gastrulation, and early organogenesis in a chick embryo
The cells in the three germ layers have
defined fates in the adult:
Topics in Development
• 1. totipotency: development depends on selective expression of
the whole genome present in every cell.
• 2. blastula to gastrula: comparative analysis yields insights into
the general nature of development
• 3. the three fundamental processes:
– cell division (differential rates of division are critical,
programmed cell death is significant)
– cell differentiation (changes in integration and shape are
critical; targeting cells with signals is a critical part of the
process)
– morphogenesis of tissues and organs (includes defining the
individual’s polarities, dividing the organism into segments,
and – in animals -- migration of cells in tissue origin)
Figure 21.4 Cell lineage in C. elegans
C. elegans cell targeting
C. elegans cell targeting
Figure 47.14 Organogenesis in a frog embryo
Figure 47.16 Change in cellular shape during morphogenesis
Apoptosis in development
Topics in Development
4. Homeotic genes
a. the determination of appendage identity
on fruitfly segments
b. the evolution of form in segmented
animals
4. Morphogenesis in Plants
5. Organ identity genes in flower development
Figure 21.11 Key developmental events in the life cycle of Drosophila
Figure 21.12 The effect of the bicoid gene, a maternal effect (egg-polarity) gene
Drosophila
Figure 21.13 Segmentation genes in Drosophila
Figure 21.13 Homeotic mutations and abnormal pattern
formation in Drosophila
Homeotic genes:the DNA sequence of the gene (blue)
contains a 180 bp sequence—the homeobox—(red) that
is highly conserved.
The homeodomain - 60 amino acids of the homeotic
gene product that remain very similar in all proteins
made by homeotic genes.
Figure 17.7 The initiation of transcription at a eukaryotic promoter
control of transcription in
C.elegans lin-3
|
tctctccctattcaatgcacctgtgtattttatgctggttttttcttgtgaccctgaa
aactgtacacacaggtgttcttaccaatgtctcaggcatttttggaaaagta
atattaagaaaattatacatattttcttgaatacgaaaaatttaaATGTTC
GGTAAATCGATTCCTGAACGACTTCTAGTCGCATTT
HLH-2 binding site
NHR binding site
EXON is in uppercase letters.
Figure 19.10 Three of the major types of DNA-binding domains in transcription
factors
The homeobox is relatively constant because it has a precise job.
The homeobox is relatively constant because it has a precise job.
Figure 21.14 Homologous genes that affect pattern formation in a fruit fly and a
mouse
Topics in Development
4. Homeotic genes
a. the determination of appendage identity
on fruitfly segments
b. the evolution of form in segmented
animals
4. Morphogenesis in Plants
5. Organ identity genes in flower development
Serial Homology of the Lobster
CRUSTACEANS COMPARED - EVOLUTIONARY HOMOLOGY
CRUSTACEANS COMPARED:
EVOLUTIONARY TRANSFORMATION
ROCK CRAB
LOBSTER
Figure 33.28 Horseshoe crabs, Limulus polyphemus
Figure 33.27 A trilobite fossil
Figure 33.x1 Insecta: beetle
Figure 32.8 Animal phylogeny based on sequencing of SSU-rRNA
lophophore
Figure 32.13x Burgess Shale fossils
Figure 32.13 A sample of some of the animals that evolved during the Cambrian
explosion
Porifera and Cnidaria are
prominent in the Burgess Shale
Annelid worms in
the Burgess shale
Anomalocaris hunts
so are arthropods!!
Figure 26.8 The Cambrian radiation of animals
Causes of the
radiation:
1. Atmospheric
oxygen reaches
sufficient levels.
525
Burgess
Shale
P
R
D
D
PL
PL
PL
PE
2. Predator-prey
relationships
originate.
3. Homeobox
genes evolve.
(Ediacaran)
Evolutionary changes in the timing of homeobox genes
yield morphological change.
Artemia, the brine shrimp
Another representation of the sequence of homeotic gene
expression in an arthropod.
Notice the continued prominence of Antp, Ubx, and Abd
paralogs.
Timing of expression of the homeobox genes Antp, Ubx,
and AbdA. Fading lines indicate weaker expression later
in development.
Number of homeobox paralogs increases in arthropods.
This illustration
also shows
change in timing
of gene
expression.
Amino acid
sequences
compared
for the
homeotic
gene Ubx
insects
arthropods
Dm - Fruitfly
Tc - Beetle
Jc - Butterfly
Ak - Onychophoran
Decides six legs versus more
Topics in Development
4. Homeotic genes
a. the determination of appendage identity
on fruitfly segments
b. the evolution of form in segmented
animals
4. Morphogenesis in Plants
5. Organ identity genes in flower development
Figure 35.13 Morphology of a winter twig
Padua Botanical Garden
Johann Wolfgang von Goethe
1749 - 1832
Goethe’s inspiration - the European
Fan Palm at the Padua Botanical
Garden
SERIAL HOMOLOGY - GOETHE’S PALM
Figure 35.17 The terminal bud and primary growth of a shoot
Figure 21.20a Organ identity genes and pattern formation in flower development:
Normal flower development
from Campbell, 6th edition
A set of homeotic genes, in different combinations, yield the different floral organs.
A
B
C
E
Figure 21.20b Organ identity genes and pattern formation in flower development: In
situ hybridization
from Campbell, 6th edition
The evolutionary determination of sepal
and petal.
A
B2 B3 C
B1
Topics in Development
4. Homeotic genes
a. the determination of appendage identity
on fruitfly segments
b. the evolution of form in segmented
animals
4. Morphogenesis in Plants
5. Organ identity genes in flower development