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Lecture 17

HMB321H1 Lecture Notes - Lecture 17: P53, Zebrafish, Stem Cell

Human Biology
Course Code
Maria Papaconstantinou

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18 MAR 2011
HMB321 L17: Introduction to Model Organisms
Why use model organisms?
-Easy to grow
-Rapidly reproduce
-Small size
-Large collections of mutants
-Genes + pathways conserved
-Genomes sequenced (easier to identify genes with mutant phenotypes)
Planarians: Flatworm (Schmidtea mediterranea)
-Key organism for studying
-Stem cell regulation
-Neuronal behaviour
-Regeneration *
-I.e. Cutting them in half will regenerate a new planarian (2 planarians)
-Study regeneration in humans, as well, e.g. Aging?
-Regeneration is not totally impossible in humans (e.g. Young children regeneration of
fingers, or hemispheres in the brain)
-Easy to grow / easy to surgically manipulate / accessible to manipulation
- Guest Lecture 1: Bret Pearson (Planarians & Cancer)
-Identified and characterized the p53 gene in planarians (Smed-p53)
Drosophila: Fruit fly
- Egg => Embryogenesis => Larva (eats to grow and develop) => instar stages (imaginal disks) =>
pupation => eclosion => Adult
- Takes 10-11 days, depending on temperature
- Features?
- Genetics / polytene chromosomes / external development
- Polytene chromosomes are long chromosomes can be used to study chromosome behaviour,
see deletions or rearrangements visually, can map specific positions of genes onto chr
- External development allows you to track developmental stages, allowing you to perform
developmental experiments
- Techniques of genetic modification?
- Forward + reverse genetic approaches
- Forward = standard mutagenesis (e.g. Chemicals such as EMS, X-rays, P-element transposon in
transgensis, targeted gene KOs with induced replacement or RNAi)
- Make mutations and analyze their mutant products function, or phenotypes
- Reverse = find mutations and assess the genetics of it
-Techniques: P-elements
- P elements are transponsons and are able to jump around the genome (with transposase)
- Can be used to either mutate endogenous genes or for gene insertion
- E.g. Insertion of ry+ (eye colour = wt = red); mutation causes pink eye
- Requires inverted repeats in plasmid surrounding ry+ in P element for
transposase to excise it from the plasmid
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