Model Organisms Flashcards
Reductionism means to
go down and specify so instead of looking at an organism you’d look at the genes
Mechanistic means that
ur not using the right phenomena and not reductionist enough so go down. not exactly relaistic cuz u need other processes for a lot stuff to work
What is the most commonly uses animal model
Rodents, predominantly mice
Mouse scientific name
Mus musculus
Who was an important and under recognized mouse fancier
Abbie Lathrop, generated many of the well known inbred mouse strains
Why are mice inbred?
To achieve consistency
Rodents as a comparative research model means
the use of one species to understand the processes a another
Why use rodents as the gold standard? 6
Similar anatomy physiology
Share 95% of genes with humans
fully sequenced genes
Can do knock-out models
Economic
Breeding is easy
Rats are
much larger than mice making stuff like surgery easier
Rats are easier to do
much larger than mice making stuff social/psych studies on cuz they’re friendly but mice are scared surgery easier
The three Rs
Replacement: Using a lower level organism (flies instead of mice)
Reduction: Reducing the amount used, someone uses the stomach another uses the brain
Refinement: minimizing pain / distress so environmental stuff and human euthanization
Rodent house misconceptions so they’re actually
very well kept they have food and water and live comfertably
- mouse is one of th emost comonly used
db/db and has a leptin receptor deletion (get fat, no stop signalling), but their sterile
the Ms4a3xAi14 model is flurescently tagged and
the monocytes from bone marrow will fluoresce
The adipochaser mouse is
a adiponectin driven thing that lets us track adipocytes in response to a stimulus
The worms got the
first sequenced genome of multi cellular organism and its much bigger than yeast
Worm scientific name
C. Elegans
In C. Elegans naming there is
3 or 4 letters followed by a - and # so unc-6 - gene
They are phylogenetically as close
to humans as any invertebrate
C. elegans are good cuz theyre simple but
complex so things seen in worms can be applicable to humans
Theyre werinf cuz they enter
meiosis on o side and do meiosis until they reah the uterus and can become like self-fertalized or real fertalized
theyre non-parasitic ad gave rapid generation time and
are transpernt and cheap and can do crispr
If a hermaphrodite self-reproduce most offspring are
hermaphrodites except 1 in 500 is male cuz of non-disjuntion and they loose an x (femal xx male xo)
They lay eggs through
the vulva
While hermaphidited are longish pointy tails, males have
like this pointy curve outer thing going (triangly)
Life cycle of C. Elegans
LEARN
Bag of worms is when
the hermaphodite doesn’t have a vulva so they cant leae so the babies eat their way out and kill mom in the process
C. Elegan methods
postional cloning (adding a specific mutation), genome sequencing, RNAi (knock out gene), RNAi by feeding (down regulation), millions mutant project and crispr
The class gastropoda is a diverse class of mollusk within the phylum
mollusca, goes back to the late cambrian
Where are snails found?
from deep ocean trenches to desert, so everywhere.
Snail scientific name
Lymnaea
Name the 6 types of learning Lymnaea have
- non-associative learning
- Associative learning
- Configural Learning
- Garcia effect
- Instinct
- Adaptation
There are strains of snails like
smart, dumb and average
Where were zebrafish originally found?
in slow streams and rice paddies in ganges rivers in India and burma
Zebrafish are closer
to humans than other fish species
So whyd they become a model organism?
70% of human genes present in zebrafish and 84% o human genes that are linked to diseases have zebrafish orthologs
What are advantages to using zebrafish - 10!
High fecundity (lots of offspring per parent)
external fertilization
transparent embyo
rapid development
small enough for passive diffusion > cardio defects
regenerative
simple vertebrate system
identifiable stereotypes neurons
easy genetic manipulation
What kind of diseases are present in both zebrafish and humans
heart, blood, eye, GI, brain/behaviour, vasculature, kidney, skeleton, Ear
What are disadvantages to using zebrafish
aquatic
complex genome (gene duplication)
lack some key organs
aquatic environment
new model
few commercial antibodies
phenotype based whole organism screening does what
identifies drug that alleviate a certain phenotype
Toxicity screenings do what
analhyze toxcicity and can be used to eliminate highly toxic compounds from stuff
Structure-activity relationships do what
check for alterations of identified compounds, and improvement or changes in specificty
Rna or dna is injected when
before fertilization?
Clevage is
2cells and rapid divisionB
blastula is
128 cels and genes trancribed, division slows
Epiboly is
blastoderm spreads and covers yolk
gastrulation is
the blastoderm develops into 2 layers by involution
Segmentation is when
somites form, primary organs start to develop
We can cause mutagens so induce the phenotype and look at affected genes, techniques for this are
radiation, cchemical exposure in water, injections
Or phenotypic screening so observe for days for morphological or behavioural diffs, techniques include:
Transgenic markers, ISH (immunostaining)
Forward genetics vs reverse genetics
find the gene causing phenotypes vs looking at phenotype cause by genetic manipulation
How many Nobel prizes for work in Drosophila?
6, started with thomas hunt morgan
Thoman Hunt Morgan First did wha
verified mendels work through drosophila
Then he found out what
sex-linked inheritance,
Most fly genes are mapped so we can
turn genes ON or OFF at any time
Their also good cuz theyr
small, reproduce quick, cheap
How many ch. do flies have?
4 ch.
u CAN KNOCK OUT USING rnaI OR dsRNA so…
U MAKE SMTH ELSE TURN ON SMTH ELSE?
Advantages
Short development time -10days
Cheap and can get a large amount quick
smaller genome
75% has human homologues
there are tools to over-express or knock-out
Disadvantages
No permanent conservation, so can only use while living
Four stages of drosophila growth
Embryo, larvae, pupae (sexual maturity) , adult
4 things that correlate between flies and humans are
Digestive tract, nervous system, body organisation, circulation-excretion-skeleton-muscles
Chicken scientific name
gallus gallus
Chicks were the first non mamallian amniote to
have their full genome sequenced in 2004
What 3 things can tissue transplantation tell us?
Instructive and permissive tissue interactions
cell determ
cell lineage
What are some advantages of chicks
cheaps
available in large numbers all year round,
develop quickly (60 days embryo to adult)
Big bibliography on systems and organ development
development resembles mammals
genome is 1/3 size of humans but has about the same amount of genes
large size - good for surgery
no ethics
Disadvantages of chicks
preblastodermal stage not easily accesible
Little research material compare to other model organisms (like antibodies and stains)
Transgenic chicks are expensive
Stage 5 has 19-22 hr
Primitve streak, hensens node and head process
stage 7 has 23-26 hrs
1st pair somites,
stage 10 has 33-38 hrs
Heart visible and functioning, 10 pairs of somites, 3 brain vesicle visible and optical vesicles
Stage 17 52-64
Limv. buds visible, leg buds larger than wings, more CNS development, branchial arched form (jaw, pharynx, larynx)
Stage 22-25 has 3.5-5days
eye pigment, limbs forming
Stage 36-37 10-11 days
Feathers visible, egg tooth stick out, eyelids form
Stage 44-45 18-20 days
Increase beak size and toe length, hatch after 21 days
What is in ovo culture good for
protected, good physio-chem, shell gives nutrients
Ex-ovo is good cuz
easily visible and easily manipulated
Viral gene transfer include
Adenoviruse and retrovirus
Non- viral includes
Nuclear micro injection, calcium ohosphate, lipofection, plasma injection, electroporation particle bombardment
