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Chapter 21
The Genetic Basis of Development
Chapter 21
The Genetic Basis of Development
Embryonic development involves:
•Cell division
•Cell differentiation
•Morphogenesis
Chapter 21
The Genetic Basis of Development
Model organisms:
Chapter 21
The Genetic Basis of Development
Model organisms:
fruit fly
Chapter 21
The Genetic Basis of Development
Model organisms:
nematode
Chapter 21
The Genetic Basis of Development
Model organisms:
zebra fish
Chapter 21
The Genetic Basis of Development
Model organisms:
common wall cress
Chapter 21
The Genetic Basis of Development
Different kinds of cells have
the same DNA
Chapter 21
The Genetic Basis of Development
Different kinds of cells have
the same DNA.
Totipotent: able to divide to
produce an entire new
organism (most plant cells,
some animal cells).
Chapter 21
The Genetic Basis of Development
Different kinds of cells have
the same DNA.
Pluripotent: able to reproduce
and differentiate in vitro and in
vivo (stem cells).
Chapter 21
The Genetic Basis of Development
Different kinds of cells make
different proteins thru regulation
of gene transcription
Chapter 21
The Genetic Basis of Development
Different kinds of cells make
different proteins thru regulation
of gene transcription.
Regulation is directed by
maternal molecules in the
cytoplasm and by signals from
neighboring cells.
Chapter 21
The Genetic Basis of Development
Pattern formation: development of
spatial organization
Chapter 21
The Genetic Basis of Development
Pattern formation: development of
spatial organization.
Continuous in plants, but for
animals it takes place only in
embryos and juveniles
Chapter 21
The Genetic Basis of Development
Pattern formation: development of
spatial organization.
Continuous in plants, but for
animals it takes place only in
embryos and juveniles.
Positional information along axes
and in relation to neighbors.
Chapter 21
The Genetic Basis of Development
Life Cycle of Drosophila
Chapter 21
The Genetic Basis of Development
Life Cycle of Drosophila
1. For the first ten cell divisions,
there is no cell growth and no
cytokinesis. You end up with one
big multinucleated cell.
Chapter 21
The Genetic Basis of Development
Life Cycle of Drosophila
2. At the tenth division, nuclei
migrate to the periphery of the
embryo.
Chapter 21
The Genetic Basis of Development
Life Cycle of Drosophila
3. At division 13, plasma
membranes finally begin to partition
the 6000 or so nuclei into separate
cells. The body plan and segments
are already determined.
Chapter 21
The Genetic Basis of Development
Life Cycle of Drosophila
4. Visible segments form. They look
very much alike.
Chapter 21
The Genetic Basis of Development
Life Cycle of Drosophila
5. Some cells move to new
positions. Organs form. The wormlike larva hatches.
The larva eats, grows, and molts
through three larval stages.
Chapter 21
The Genetic Basis of Development
Life Cycle of Drosophila
6. The larva forms a pupa in an
enclosed case.
Chapter 21
The Genetic Basis of Development
Life Cycle of Drosophila
7. Metamorphosis occurs inside the
pupa. When the adult hatches, each
segment is anatomically distinct.
Chapter 21
The Genetic Basis of Development
Egg polarity genes
Chapter 21
The Genetic Basis of Development
Egg polarity genes are
“maternal effect genes”
Chapter 21
The Genetic Basis of Development
Egg polarity genes are
“maternal effect genes.”
They produce proteins called
morphogens
Chapter 21
The Genetic Basis of Development
Egg polarity genes are
“maternal effect genes.”
They produce proteins called
morphogens.
A morphogen gradient
establishes the anteriorposterior axis.
Chapter 21
The Genetic Basis of Development
Bicoid is a gene in the mother
that produces a two-tailed
offspring.
Chapter 21
The Genetic Basis of Development
Segmentation genes act in a
cascade, directing the
formation of segments
Chapter 21
The Genetic Basis of Development
Segmentation genes act in a
cascade, directing the
formation of segments.
Their products are
transcription factors for other
genes.
Chapter 21
The Genetic Basis of Development
Segmentation genes act in a
cascade, directing the
formation of segments.
Their products are
transcription factors for other
genes.
Chapter 21
The Genetic Basis of Development
Homeotic genes control the
growth of specific organs.
Chapter 21
The Genetic Basis of Development
gene
function
maternal effect
egg polarity
segmentation:
•gap
•pair-rule
•segment polarity
coarse subdivision
further subdivision
orientation of seg’s
homeotic
specific organs
Chapter 21
The Genetic Basis of Development
gene
function
maternal effect
egg polarity
Chapter 21
The Genetic Basis of Development
gene
function
maternal effect
egg polarity
mutation
Chapter 21
The Genetic Basis of Development
gene
function
gap
coarse subdivision
Chapter 21
The Genetic Basis of Development
gene
function
gap
coarse subdivision
mutation
Chapter 21
The Genetic Basis of Development
gene
function
pair-rule
further subdivision
Chapter 21
The Genetic Basis of Development
gene
function
pair-rule
further subdivision
mutation
Chapter 21
The Genetic Basis of Development
gene
function
segment polarity
further subdivision
Chapter 21
The Genetic Basis of Development
gene
function
segment polarity
further subdivision
mutation
Chapter 21
The Genetic Basis of Development
gene
function
homeotic
specific organs
Chapter 21
The Genetic Basis of Development
gene
function
homeotic
specific organs
mutation
Chapter 21
The Genetic Basis of Development
Homeobox (hox) genes have
been highly conserved
Chapter 21
The Genetic Basis of Development
Homeobox (hox) genes have
been highly conserved.
Chapter 21
The Genetic Basis of Development
Neighboring cells instruct other cells
to form particular structures
Chapter 21
The Genetic Basis of Development
Neighboring cells instruct other cells
to form particular structures.
nematode
gonad
vulva
Chapter 21
The Genetic Basis of Development
gonad
vulva
Chapter 21
The Genetic Basis of Development
epidermis
outer vulva
inner vulva
gonad
vulva
Chapter 21
The Genetic Basis of Development
anchor cell
precursor cells
Chapter 21
The Genetic Basis of Development
The anchor cell secretes a first inducer
Chapter 21
The Genetic Basis of Development
The anchor cell secretes a first inducer.
The inducer binds to receptors on the nearest
cell (where the concentration is highest)
Chapter 21
The Genetic Basis of Development
The anchor cell secretes a first inducer.
The inducer binds to receptors on the nearest
cell (where the concentration is highest).
That cell begins to develop into the inner
vulva
Chapter 21
The Genetic Basis of Development
The inner vulva cell secretes a second
inducer
Chapter 21
The Genetic Basis of Development
The inner vulva cell secretes a second
inducer.
The second inducer binds to receptors on
neighboring cells
Chapter 21
The Genetic Basis of Development
The inner vulva cell secretes a second
inducer.
The second inducer binds to receptors on
neighboring cells.
They begin to develop into outer vulva.
Chapter 21
The Genetic Basis of Development
If you surgically remove the anchor cell from
the embryo, the nematode develops without a
vulva.