Model organisms

Question 1

What are the model organisms?

Answer 1

• ‘the worm’
• ‘the fly’
• Echinoderms, amphioxus and sea squirts- Deuterostome invertebrates
• Vertebrate models

Question 2

The tree of (animal) life

Answer 2

Question 3

What are the developmental patterns among metazoan

Answer 3

• Diploblast
• Triploblast
• Protostome
• Coelom schizocoely
• Ecdysoan
• Lophotrochozoan
• Deuterostome
• Coelom enterocoely
• Spiral vs radial cleavage

Question 4

What are diploblast?

Answer 4

two cell layers (endo- and ectoderm (germ layer on the outside of the embryo that forms the skin and nervous system)

Question 5

What are Triploblast?

Answer 5

three primary germ layers; ectoderm, mesoderm giving rise to muscle and skeletal system and endoderm

Question 6

Snails

Answer 6

Question 7

Tell me the coiling in snail shells?

Answer 7

• 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

Question 8

Nematodes, C. elegans

Answer 8

Question 9

‘the fly’, D. melanogaster

Answer 9

Question 10

‘the fly’, D. melanogaster

Answer 10

Question 11

‘the fly’, D. melanogaster

Answer 11

Question 12

Deuterostome invertebrates

Answer 12

Question 13

Echinoderms

Answer 13

https://www.youtube.com/watch?v=sq-BY-JpPaM

Question 14

Echinoderms

Answer 14

Question 15

Sea squirts

Answer 15

http://www.youtube.com/watch?v=rZyZeml9oyM

Question 16

Historical observations of body plans

Answer 16

Question 17

Disparate adult forms, but similar developmental starting place

Answer 17

Question 18

Vertebrate models

Answer 18

Question 19

Fish models

Answer 19

http://www.youtube.com/watch?v=A1vun3ETAkE

Question 20

Amphibian models

Answer 20

Question 21

Amphibian models

Answer 21

Question 22

Birds and mammals

Answer 22

Question 23

Hox genes

Answer 23

Question 24

Human models

Answer 24

• 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

Question 25

What are pros and cons of model organisms?

Answer 25

**Pros:** Lab friendly Quick generation time Learn more about evolutionary history **Cons:** Unusual compared with other organisms Taxon specific development Not completely representative

Question 26

**summary**

Answer 26

* **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**