Following statements are regarding to anterior-posterior polarity in planaria.

A. The anterior expression of Notum functions to antagonize the posteriorly produced Wnt, leading to head specification.

B. Regulation of the balance between Wnt and Notum signals may underlie not only head-tail specification but also regulation of organ size.

C. In addition, there appears to be an anterior-to-posterior gradient of Erk signaling that functions as a positive inducer of tail specification.

D. Wnt signaling achieves its repression of head regeneration by inhibiting Erk. Therefore, only in those more anterior regions lacking Wnt (due to Notum’s repression of Wnt) can Erk induce head regeneration.

Which of the following statements are incorrect?

#Question id: 7116

#Unit 5. Developmental Biology

Which one statement best describes gastrulation in sea urchins?

a) Gastrulation is initiated by invagination of the micromeres at the vegetal pole.

b) The mouth of the pluteus larva will form from mesomeres on the oral side of the 60-cell embryo.

c) The gut will form from the macromeres at the 16-cell stage.

d) Mesenchymal cells originating at the vegetal pole will invaginate first during gastrulation and will form skeletal structures in the pluteus larva.

Which of the following combination is correct?

#Question id: 7117

#Unit 5. Developmental Biology

Which of the following statements explains why gain-of-function mutation of Pmar1 results in a vegetalized embryo:

#Question id: 7118

#Unit 5. Developmental Biology

At the molecular and cellular level, how does morphogenesis differ from establishment of embryonic axes and the specification of cellular identity?

#Question id: 7119

#Unit 5. Developmental Biology

Adherens junctions play in important role in development; they are composed of:

#Question id: 7120

#Unit 5. Developmental Biology

Which of the following is the only true statement regarding compaction in the mouse embryo?

#Question id: 7121

#Unit 5. Developmental Biology

How do the endodermal cells of the sea urchin embryo carry out gut formation during gastrulation?