Transcript Chapter 13, Genetic Control of Development

Chapter 13
Genetic Control
of Development
Jones and Bartlett Publishers © 2005
• How do cells choose which type of cell to
become during embryonic development?
• The first few embryonic cells give rise to all
other cells. They are called totipotent, or
pleuripotent.
• Cell fate decisions result in differentiation
into all cell types in an organism.
Early stages in the development of an animal
Developmental processes
• Cell-autonomous developmental restrictions
– Common in C. elegans
• Positional information / intercellular
signaling
• Morphogen- a molecule the participates
directly in control of growth and
development.
Use of cell transplantation during early
embryonic development to ascertain the
timing of fate determination
The first 3 divisions during the development
of the worm Caenorhabditis elegans
Transplantation of extra cells during early
development of sea urchin results
in abnormal development
A female worm Caenorhabditis elegans
There are two kinds of worms- hermaphrodites (XX) and
males(XO). 60 hours from egg to adult (at 20 C), 300 eggs
produced in a few days, 10,000 on a petri plate. Transparent
bodies have 959 somatic nuclei.
A cell lineage diagram showing a cell that
undergoes programmed cell death (apoptosis)
and three that become differentiated
Types of developmental mutations
• Transformation mutations
• Segregation mutations
• Execution mutations
Comparison of the wild type differentiation
pattern with that of a transformation mutant
Comparison of the wild type cell division pattern
with that of a segregation mutant
Comparison of the wild type cell division
and differentiation pattern
with that of an execution mutant
The lineage of the cells Z1.ppp and Z4.aaa
P0 is the fertilized egg
“p” and “a” stand
for posterior and
anterior cells in a
lineage
The effects of ablation (destruction) or a recessive
(or dominant) mutation in the lin-12 gene
on the fate of Z1.ppp and Z4.aaa cells
The protein coded by the lin-12 gene
is a membrane receptor
Activation of a cell surface receptor and cell-to-cell
signaling is required for proper vulval development
Time scale (at 25oC) of stages in the development
of an adult Drosophila from a fertilized egg
Very early steps in the development
of Drosophila embryo
Fate map of Drosophila blastoderm
The segmentation pattern of Drosophila larva
Sites in the Drosophila larva where the
3 classes of segmentation genes are expressed
Anterior-posterior organization of Drosophila
and the genes controlling it
Segments in the larva and the adult
parts they generate
Location of the imaginal discs in the larva and
the parts they generate in the adult Drosophila
Uniform pattern of vestigial expression in the
wing imaginal disk
Evolutionary scheme by which the Ubx homolog
expressed in segment T3 produces different
developmental pathways
The flower in Arabidopsis thaliana
is organized in 4 whorls
Whorls in which Arabidopsis genes
controlling flower parts are expressed