What can you conclude about a species heavily reliant on diffusible morphogens in early development?

Question

A.  They are likely to have incomplete cleavage (a syncytium).
B.  They are likely to lack an organizer.
C.  They are likely to have activation via a calcium wave.
D.  They are likely to have small amounts of yolk and holoblastic cleavage.
E.  They are likely to have incomplete cleavage (a syncytium).


Clarify Question
What is the key concept addressed by the question?

What type of thinking is required?


Gather Content
What do you already know about morphogens? What other information is related to the question?


Choose Answer
Given what you now know, what information is most likely to produce the correct answer?


Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
 

Answer 1

A.  They are likely to have incomplete cleavage (a syncytium).
E.  They are likely to have incomplete cleavage (a syncytium).


Clarify Question
What is the key concept addressed by the question?
     · This question is asking about the role of morphogens in early development.

What type of thinking is required?
     · Apply level:
       o You are being asked to take what you already know and use, or apply, it to the consequences of diffusible morphogen activity.


Gather Content
What do you already know about morphogens? What other information is related to the question?
     · Insects have yolk rich eggs and a syncytial blastoderm, in which multiple mitotic divisions of the nucleus occur in the absence of cytokinesis.
     · Because there are no membranes separating the early embryonic nuclei of insects, gradients of diffusible proteins termed morphogens within the egg’s cytoplasm can directly and differentially affect the activity of these embryonic nuclei, and thus the pattern of the early embryo.
     · The nuclei eventually migrate to the periphery of the egg, where cell membranes form around each nucleus.


Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
     · Insects have yolk rich eggs, so holoblastic cleavage is not typical.
     · Morphogens are released from organizers, so this answer can be disregarded.
     · The calcium wave plays a role in fertilization.
     · Insect eggs are likely to have incomplete cleavage due to the abundance of yolk contained within the egg.


Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
     · Apply level:
       o Answering this question correctly depended on your ability to use morphogens in a new situation. If you got an incorrect answer, did you remember that insect eggs are rich in yolk, or that the yolk would interfere with holoblastic cleavage?