Question 6:  Stained limbs. [6 marks].

Place an Alcian-blue stained chicken embryo under the dissecting microscope. Examine the forelimb (wing) of one of the stained embryos and take a photo.

Label the humerus, radius, ulna,  phalanges.   (No need to label metacarpus ) (Upload your image)  (4 marks)

On the uploaded image , answer this question:  How many digits (phalanges) does the chicken embryo have on the forelimb?  (2 marks).

Question 5:  Alcian Blue stained chicken embryos. [2 marks].

Question 4:  The rationale for your hypothesis. [6 marks].

What type of cells form the ZPA, epithelial or mesenchymal cells ?   (1 mark)

Where is the ZPA located? (1 mark)

Why is it significant ?  (1 mark)

What critical signalling factor does it produces?  (1 mark).

What germ layer does it derive from ?  (1 mark).

How could you show that you had successfully removed the ZPA at the end of the experiment?  (1 mark).

Question 3:  An hypothesis. [2 marks].

• Eye 
• Forebrain
• Midbrain
• Hindbrain 
• Neural tube
• Heart
• Somites 
• Forelimb buds
• Hindlimb buds

b) For your embryo, determine the developmental stage (Hamburger and Hamilton stage) (1 mark)

Up-load image 

Question 1:  Examination of a day 1.5 embryo.  [6 marks].                                                                            

• Photograph and label the Embryonic day 1.5 embryo. (1 mark).
• Label the forebrain, hindbrain, neural tube, somites.  (4 marks).
• Determine the developmental stage of the embryo. (1 mark). (see page 37 for Hamburger and Hamilton (HH) stages)

Question 12: 

Your results of the mouse lung study demonstrate that expression of Vegf (Vascular endothelial growth factor) is restricted to the posterior region of the lung epithelial buds.  Your supervisor is very excited about your findings and it is decided that a lung specific Vegf knockout should be generated using a mouse model.  

Explain the process by which you would generate such a knockout (ie. the steps involved). Use a diagram.  

[10 marks; 2 marks for overall diagram, and 2 marks each for  FOUR major steps. Include at the final step what happens genetically.]

(HINT: see Craig’s lecture on mouse models!)

Question 2:  Features of a mouse embryo. [10 marks].  

Take a photo of the mouse embryo. State the embryo age, and label the following features: Forelimb bud, hindlimb bud, forebrain, midbrain, hindbrain, branchial arches, eye, heart, and somites.                                                                                       [10 marks - 1 mark for the image, 9 marks for the labels]

MOUSE PRACTICAL: PART B: 

Question 7:  LacZ stained embryos [6 marks]. 

Take a photo of a stained embryo, showing areas stained with the LacZ solution. NOTE: You may present an image of another embryo if yours does not show LacZ staining.  What major tissues are stained? Label these structures. (6 marks – for correct labelling of at least 3 stained structures; 2 marks each0.

Question 6:  Experimental scenario [10 marks].

b) Imagine you have identified a novel gene using the approach in (a) above. How might you test if this gene has a conserved role in zebrafish vertebral column development?  Without using a diagram, outline a method and the expected outcome.  (4 marks).