Model organisms Flashcards
What are the model organisms?
- ‘the worm’
- ‘the fly’
- Echinoderms, amphioxus and sea squirts- Deuterostome invertebrates
- Vertebrate models
The tree of (animal) life
What are the developmental patterns among metazoan
- Diploblast
- Triploblast
- Protostome
- Coelom schizocoely
- Ecdysoan
- Lophotrochozoan
- Deuterostome
- Coelom enterocoely
- Spiral vs radial cleavage
What are diploblast?
two cell layers (endo- and ectoderm (germ layer on the outside of the embryo that forms the skin and nervous system)
What are Triploblast?
three primary germ layers; ectoderm, mesoderm giving rise to muscle and skeletal system and endoderm
Snails
Tell me the coiling in snail shells?
- Genes that pattern the ‘handedness’ of the snail shell also pattern left/right asymmetry in human development
- Snails have spiraling symmetry- left or right-handed coiling of the snail
- Genes that control the spiraling are the same genes that set up the left/right symmetry in vertebrates/ invertebrates
- Most snails are right-handed
- Snails are hermaphrodites
- Left-handed snails can’t reproduce unless find an equally left sided female due to where the genitals are located
- Example of Jeremy the left-handed snail gave birth to 52 right-handed offspring, so it’s a developmental outcome rather than genetic
Nematodes, C. elegans
‘the fly’, D. melanogaster
‘the fly’, D. melanogaster
‘the fly’, D. melanogaster
Deuterostome invertebrates
Echinoderms
https://www.youtube.com/watch?v=sq-BY-JpPaM
Echinoderms
Sea squirts
http://www.youtube.com/watch?v=rZyZeml9oyM
Historical observations of body plans
Disparate adult forms, but similar developmental starting place
Vertebrate models
Fish models
http://www.youtube.com/watch?v=A1vun3ETAkE
Amphibian models
Amphibian models
Birds and mammals
Hox genes
Human models
- The moment of conception. The pronuclei fuse
- Following by the first division of the egg cell
- after several more divisions, the new embryo forms the bastula (hollow ball of cells)
- by 6 weeks, the embryo has a heart, eyes, a NS and limb buds
- attached to the embryo is the yolk sac which will nourish it until the plaencta is fully developed
- The yolk sac is still present at 8 weeks, the embryo now has fingers, toes and a face
- by 12 weeks the yolk sac has gone and the embryo is beginning to make rudimentary movements
- at 6 months the foetus is now almost fully developed. it simply needs to grow in the safety of the mothers womb
- movements are now strong
- by 9 months, the foetus is ready to be born
What are pros and cons of model organisms?
Pros:
Lab friendly
Quick generation time
Learn more about evolutionary history
Cons:
Unusual compared with other organisms
Taxon specific development
Not completely representative
summary
- You will now have an appreciation of:
- What are model organisms?
‘the worm’
‘the fly’
Echinoderms, amphioxus and sea squirts- Deuterostome invertebrates
Vertebrate models
- Similarities and differences across model organisms
- How are model organisms used?
- Ethical dilemmas
