HMB265H1 Lecture Notes - Lecture 20: Pax6, Mutagen, Body Plan
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HMB265 - Lecture 20
Model organisms - why are they chosen?
Easy to grow in lab
Large collections of mutants with developmental defects maintained in stock centers
Genes and pathways are conserved
Easier for geneticists to identify genes with mutant phenotypes
How relevant is the information gain from drosophila to understanding human development
when there is a giant evolutionary difference?
A lot of genes and basic strategies of development are conserved across multi-cellular
Commonalities found across very different species
Pax-6 and Aniridia wild-type genes can direct eye development in drosophila
(these genes are found in humans)
These genes can be knocked out in drosophila and replaced with the
human alleles, saving the phenotype. This is very surprising given
the difference in morphology and evolution between drosophila flies
An individual with 1 defective copy of Aniridia have defects in the iris - can cause reduction in
sharpness of vision, and cause greater sensitivity to light. It is an autosomal dominant condition.
The homozygous condition is lethal and cause
Once you have knocked out the gene, you can observe the phenotype and make conclusions on
development based on the observations you make.
In the opposite direction, you can expose a mouse to a mutagen and screen the progeny (at the
level of the phenotype) for differences and identify a mutated gene
These techniques are not restricted to studying development, but they are very successful for this
Drosophila have been important in understanding the basic body plan in animals. One of the
huge advantages of studying an invertebrate is the ease of identifying developmental mutants due
to the clear exoskeleton.
Used a novel screen to identify different genes that
The screen divided maternal genes and zygotic genes. Maternally required genes are expressed in
the egg before the
Mutations in these genes display a mutant phenotype in the