Anterior- posterior axis formation

Question 1

Which cells migrate first during convergent extension?

Answer 1

The anterior endoderm (pharyngeal) cells migrate first, followed by the prechordal mesoderm. They mark the future anterior part of the embryo

Question 2

What happens in the chick embryo as the node regresses posteriorly?

Answer 2

The posterior nervous system (hindbrain and spinal cord) develop
Axial mesoderm is laid down behind the node

Question 3

Which signals give cells posterior identity?

Answer 3

Retanoic acid and FGF

Question 4

Where are BMP antagonists secreted from- and what do they do?

Answer 4

Secreted from the organiser- inducing somites in the axial mesoderm and neural identity in overlying ectoderm
The organiser dorsalises and patterns adjacent mesoderm