Biology 205 problem set A: Development; Gene expression; Fertilization; Cell potential

*answer to be handed in in recitation sections, week of March 3rd

 

1) How might each of the following be important for normal development of an organism?

 

            i) transcription factors

            ii) promoters of genes

            iii) cytoskeleton

            iv) cell surface proteins

 

2) For each of the following techniques for detecting gene expression, a) what is the probe, and b) what substrate does the probe recognize?

 

            i) Southern blot

            ii) Northern blot

            iii) Western blot

            iv) in situ hybridization

            v) microarray

 

3)  a) Which of the following cells is arrested part way through cell division:

                        i) mammal sperm cell before fertilization

                        ii) mammal egg cell before fertilization

            b) At what stage is the cell you indicated arrested?

 

4)  Put the following events associated with fertilization in the correct sequence:

 

            fusion of egg and sperm cell membranes

            the acrosomal reaction

            binding of galactosyltransferase to the ZP3 protein

            mitosis

            meiosis

            release of cortical granules to the zona pellucida

 

5)  Describe a membrane fusion event that occurs:

 

            a) when a sperm encounters the zona pellucida of an egg

            b) once a sperm encounters the egg plasma membrane

            c) upon fertilization of the egg by a sperm

 

6)  A mature egg (not yet fertilized) is microinjected with one of the following.  In each case, will sperm introduced after the microinjection fertilize (fuse with) an egg injected with the indicated substance?

                        a) Ca++ ions

                        b) Ca++ ions and EGTA together

                        c) IP3 [note: IP3 binds ER calcium channels and causes Ca++ release.]

 

*7)  An experimentalist is studying the developmental potential of different cells (and their nuclei) in a frog species.  To do this, she tests i) whether cells from frog embryos or adults can develop into another frog when separated from the rest of the animal, and ii) whether the nuclei from such cells can direct development if transferred to an enucleated egg. 

            a) What will the indicated cell grow into after each of the following manipulations?

                        i) A frog skin cell is isolated and allowed to grow.

                        ii) A blastomere (a cell from the blastula) is isolated and allowed to grow.

                        iii) An oocyte is enucleated, the nucleus from a skin cell is introduced into it, and the resulting cell allowed to grow.

                        iv) An oocyte is enucleated, the nucleus from a blastomere is introduced into it, and the resulting cell allowed to grow.

                        v) A skin cell is enucleated, the nucleus from a fertilized egg is introduced into it, and the resulting cell allowed to grow.

b) What do these results suggest about the developmental potential of skin and blastula cells (and their nuclei)?

            c) Which is more important for directing accurate frog development, the nucleus or the cytoplasm of the egg?

 

8)  a) Dolly the cloned sheep received its egg from one parent, the nucleus in that egg from another parent, and was carried to term by a third parent.  Which of these three "parents" did Dolly resemble most closely? 

            b) Dolly is female.  How could you alter the protocol to clone a male sheep?

 

9)  a) A wealthy horse breeder wants to clone his favorite racehorse, and enlists your help because you are a renowned developmental biologist.  How would you go about cloning the horse?

 

b) If you are successful, will the cloned horse win as many races as the original?  Why or why not?

 

10) How could you distinguish neuron cells from skin cells?  Is it necessary to wait for them to differentiate to tell pre-neurons from pre-skin cells?