Model organisms, development and disease Flashcards
Two proteins are homologous if
they have a common
ancestor, whatever their sequences, structures, or functions.
Homology = common ancestry
C. elegans model for
animal longevity: the clk gene
controls repsiration, behavior and aging
MAPK signalling cascade
identification of genes involved in the S. cerevisiae mating cycle (STE mutants)
used for the mating response similar to the glycerol synthesis
Sevenless
in the Drosophila eye
Sevenless is an RTK: its over-expression
directs the generation of too many R7 cells,
which disrupts eye morphology
Sevenless
+++
w/one copy
of suppressor
Loss of a single copy of a gene downstream, restores eye morphology •Dominant, with a single copy lost! •Allows straightforward F1 screen •The eye is not essential for viability
The EGFR RTK/Ras signalling pathway
major player in several cancers
cause active Ras and downstream signals
The P-element
Allows mutagenesis, by trans-complementation of
the transposase, extremely useful to tag mutations
Allows identification of the mutation site through
basic molecular biology techniques, such as allaround pcr, or RACE.
Can be used to transform, and express transgenic
copies of genes
Induced mutations in Drosophila have three categories
Gap, Pair-rule, segment polarity
Gap - kruppel (stem cell regulator KLF4 in vertebrates)
Pair-rule
Absence vs presence of Wnt in signalling pathway
absence = target gene expression repressed
present = activated
The Sonic Hedgehog (Shh) signaling pathway in presence and absence of SHH
when Shh not there Ptch 1 represses SMO and thus repressed target genes
When SHH is there, it prevents repression, activate target genes
Cyclopamine
is a natural inhibitor of Smo
found in the plant Veratrum californicum
The BMP signaling pathway
• BMP binding to Receptor complex activates
Serine/Threonine kinase activity of type I receptor
Hox genes
control the differentiation
of the segment where they are expressed
in different segments to provide identity Hox proteins are transcription factors (gene regulatory proteins) Hox proteins provide the positional identity to the cells they are expressed in Evolutionary conserved – Found in all bilateria (from sea urchin to humans) First identified in Drosophila (Homeotic transformations)
Ultrabithorax (Ubx) mutant
wings in haletres location
Colinearity
The alignment of genes along
the chromosome corresponds with their
expression pattern along the embryo
Pink: anterior-most expression followed by
green, dark blue, light blue, red and olive.
Combinatorial activity
It is the combination
of transcription factors (Hox proteins) that
provides cell identity, rather than a single one
