lecture 3- model systems Flashcards
what is a model system
a system, area, or organism that is simple and informative to work with that applies to other systems, areas, or organisms
model system (organism) definition
an organism studied in great detail as a representative of other organisms similar to it
- genetic model organism: a representative organism from a genetic perspective, such as simple genome or well studied genetics
- developmental model organism: a representative organism from a developmental perspective, with similar developmental processes that are easy or well to study
what makes a good model system GENERALLY
easy to use or study
ease of data generation (easy to study genotypes and phenotypes)
readily available
strong link of results applying to related systems
used by many researchers
what makes a good GENETIC ORGANISM model SPECIFICALLY?
short generation time
small size (to grow more in one place)
large numbers of progeny produced
ability to follow genetics (track phenotypes generation to generation)
genetic manipulation (ease of mutation, ease of ability to generate transgenics, molecular tools available)
genome sequence and annotated (what the genes are)
link to relevant processes- development
link to economic importance
what makes a good DEVELOPMENTAL ORGANISM model SPECIFICALLY?
short generation time
ability to have large numbers for examination
ease of ability to examine developmental processes
ability to manipulate development
genetic model commonalities (ability to identify specific factors involved)
what makes a good DEVELOPMENTAL GENETIC ORGANISM model?
specifically- must combine strong characteristics of both genetic and developmental systems
- there are both great genetic models without interesting development and great developmental system without good genetics
name 7 major developmental genetic model organisms
( Sacch. cerev. (yeast))
- Caenorhabditis elegans (worm-nematode)
- Drosphilia melan. (fruit fly)
- Danio rerio (zebrafish)
- ( Xenopus laevis (frog))
- Mus musculus (mouse)
- Arabidopis thaliana (plant)
describe worm-nematode (C. elegans)
short life cycle 2-3 weeks (12 hr. embryogenesis, 2-4 day generation time)
small size (1 mm)
easy to care for (raise on petri dish)
lots of progeny (300+ by fertilization)
describe worm-nematode (C. elegans) more features
- great genetics & lots of mutants
- relatively small (100 Mb), sequenced genome
- 35% of (20,500) genes have human analogs
- lots of molecular techniques available (RNAi interference)
- complete lineage of all 959 cells known (complete fate map)
- clear body to observe internal structures
list the limitations of C. elegans
embryonic manipulations difficult
- small & rapid
no homologous recombination (gene for gene replacement), but there is CRISPR
not very similar to humans, only 35% are human analogs (also its a worm)
describe fruit fly (Drosphilia)
insect model system
life cycles change depending on temp
short generation time (10 days)
small (3 mm)
ease of care
100 years of research (well studied development)
multiple developmental life stages (embryo, larva, pupa, adult)
describe fruit fly (drosphilia) more features
- great genetics
- sequenced genome
- 15,680 genes and 60% with human analogs
- lots of molecular tools
. tons of mutants (EMS, transposons, P-elements)
. transgenics (RNAi) - quite similar to humans in neural development pathways
list limitations of fruit fly (drosphilia) as model organism
must maintain stocks- generation to generation
difficult to manipulate embryos
still not a human (invertebrate)
gene copy number differences (fly single copy, human multiple copies)
describe zebrafish (Danio rerio)
small (2-4 cm), rapidly developing vertebrate
easy to maintain
lots of transport embryos (200-300 eggs a day)
mutants
RNAi
sequenced genome (27000 genes)
70% of genes have a single human analog
list the limitations of zebrafish (D. rerio)
- relatively “new” model system
- growing transgenic resources
- ~3 month generation time
- no homologous recombination (but CRISPR)
