development

Question 1

morphogen

Answer 1

a signalling molecule that regulates the pattern of tissue development during embryonic development

Question 2

signalling centre

Answer 2

a localised group of cells that produce and release signalling molecules such as morphogens or growth factors to regulate the development and patterning of surrounding tissues

Question 3

zone of polarising activity

Answer 3

a specialised region of tissue at the posterior margin of the developing limb bud of the vertebrate limb.
plays a crucial role in establishing the anterior-posterior axis of the limb

Question 4

apical ectodermal ridge

Answer 4

a critical structure at the distal end of the developing limb bud in vertebrates
plays a vital role in limb development by regulating the growth and patterning of the limb along its proximal-distal axis

Question 5

axes of the vertebrate limb

Answer 5

1. proximal-distal axis
   - proximal > part of the limb closer to the body
   - distal > part of the limb farther from the body
2. anterior-posterior axis
   - anterior > side of the limb closest to the body’s front
   - posterior > side of the limb closest to the body’s back
3. dorsal-ventral axis
   - dorsal > the back or top of the limb
   - ventral > the palm or sole of the limb

Question 6

main signalling centres involved in the patterning of the vertebrate limb

Answer 6

Apical ectodermal ridge
- proximal-distal axis
- removal of AER from developing chick limb buds = cessation of limb growth
zone of polarising activity
- anterior-posterior axis
- transplant of ZPA tissue from the posterior limb to the anterior limb = duplication of digits
dorsal-ventral patterning