BIO 3220 Final Exam Name___________________________________ Spring 2010
Choose two (2) questions to work for your final exam. Each question is worth 50 points and you can
write a maximum of one page for each answer. The exam is due by 5 pm on Monday May 3rd.
1) 50 pts. Describe the major signals that are responsible for kidney formation in the embryo and
how they contribute to kidney formation. Predict what will happen if the cells of the nephric duct
do not express the Ret receptor and how you would confirm, experimentally, that these cells did
not have the protein.
2) 50 pts. What is the apical ectodermal ridge (AER)? Predict the phenotype that would result if (a)
you removed the AER from one side of an embryo? (b) You transplanted a second AER adjacent
to the AER on one side of an embryo? (c) if you replaced the AER on one side of an embryo with
a bead that contained FGF? (d) if you divided the AER into 2 separated fields by inserting a small
plastic shield right down the middle of the limb bud? Design an experiment to determine whether
the apical ectodermal ridge, or the underlying mesoderm, is responsible for the identity of the
structures that differentiate in the limb (in other words, does the AER or the underlying mesoderm
contain the instructions for the differentation of the humerus?).
3) 50 pts. Draw a cross section depicting the neural tube, notochord, somites, and lateral plate
mesoderm of an embryo. What are the major signals produced by these tissues that affect the
differentiation of the somite? Indicate their origin and action on the diagram. Predict the effect of a
SHH knockout on the differentiation of the sclerotome and tell me why.
4) 50 pts. This figure shows a scanning electron micrograph of the paraxial
mesoderm and neural tube of a chick embryo. What is the molecular
mechanism that has been proposed to account for how each somite can be
created out of the single long block of paraxial mesoderm? Describe an
experiment that would demonstrate this mechanism in the embryo.
5) 50 pts. Describe how the following signals interact to affect sex
determination of a person who has a genotype of XX? What about XY?
Explain what happens if a person with an X and Y chromosome also has an extra copy of DAX1?
SRY, SF1, SOX9, DAX1, and WNT4.
Question 4
