CTB 7 – Evolutionary genetics of craniofacial strictures Flashcards
What is a cephalochordat?
- e.g. amphioxus - marine animal
- headless and jawless
- filter feeder
- primitive
What is a cyclostomata?
- circular with primitive teeth
- e.g. lamprey
- primitive head and jawless
- have neural crest cells
- Movement – occipital and parachordal carts and arch 0 to the neurocranium to form the skull base and head to support brain and organs
What is the gnathostomata?
- E.g. fish, amphibians, reptiles, mammals… etc
- Jawed
- Arch 1 transform into jaw with articulated joint- predator
In fish, what bone suspends the jaw?
Hyomandibular bone
What do the hyomandibular bones become in amphibians, birds and reptiles?
Quadrate and the articular bone – form a bone joint and enable primitive hearing
What jaw movements do amphibians, birds and reptiles have?
Up and down
Within mammals what do the quadrate and articular bones internalise to form a part of?
Forming part of the middle ear – malleus and incus joint
What jaw movements do mammals have?
Sideways
Why do birds have no teeth?
To have less weight, so they can fly, bones are also very thin and light – no PAX 9
Where is the future tooth shape determined from?
Primary enamel knot
What gene is suppressed in hyperdontia to stop an additional tooth row?
Inhibition of Bmp4