1. (2 points)  The following are examples of developmental processes.  Which of these processes does not involved regulative mechanisms?

 A.  determination of cell identity within a Drosophila segment
 B.  determination of segment identity in Drosophila
 C.  induction of nervous system formation by chordamesoderm
 
 

2. (5 points).  Match the class of Drosophila developmental genes with the best description of their function.

maternal effect genes
gap genes
pair rule genes
segment polarity genes
segment identity genes

A.  These genesí products divide the embryos into large regions consisting of several segments.
 

B.  These genesí products determine the anterior and posterior fate of each cell within the segment.
 

C.  These genesí products form gradients in the early embryo that determine anterior posterior pattern of the embryo.
 

D.  These genesí products give each segment itís abdominal or thoracic characteristics.
 

E.  These genesí products divide the animal into parasegments.
 
 
 

3.  (2 points)  A new mutant is discovered in Drosophila.  As a homozygote it is an embryonic lethal, mutant embryos appear to be missing every other parasegment of the animal.  When this mutant is combined with a ftz reporter construct, lac Z expression is altered.  This mutant is most likely
 A.  a new secondary pair rule gene
 B.  a new primary pair rule gene
 C.  a new gap gene
 D.  a new segment polarity gene
 E.  a new segment identity gene
 
 

4.  (5 points)  Match the class of genes to a picture below that best describes their expression pattern just after cellularization of the Drosophila blastoderm. (pictures are taken from figure in the book)

A.  maternal effect genes
B.  gap genes
C.  pair rule genes
D.  segment polarity genes
E.  segment identity genes
 

5.  (2 points)  The gap genes control the expression of individual stripes of the primary pair rule genes by
 A.  binding as both repressors and activators to stripe-specific enhancer regions of the           primary pair rule genes
 B.  acting as repressors of pair rule gene expression in the region they are expressed
 C.  altering the chromosome structure in cells expressing certain pair rule genes
 D.  setting up regulative interactions between cells expressing various pair rule genes
 E.  all of the above
 

6. (10 points)  Answer question A or B below

A.  Describe how the genes, bicoid, hunchback, nanos and caudal act to set up the gradients responsible for anterior posterior patterning in the early embryo.

B.  HOX genes are evolutionarily conserved in their chromosomal organization, their relative expression pattern and their role in segmentation.  Describe the similarities between organization of these genes and their expression in Drosophila and mouse.  Describe experimental evidence that supports that the functional role of the HOX genes in determining segment identity has been conserved between Drosophila and mouse.
 
 

10.  (10 points)    How does the gradient of retinoic acid induce a specific pattern of HOX gene expression?  Please describe events during gastrulation and as well as the molecular details behind HOX gene induction.  What types of defects would you expect if you added a high concentration of retinoic acid to an embryo during regression of Hensenís node?
 
 

12. (2 points)  Which of the following is not a function of hedgehog or sonic hedgehog
 
 A.  responsible for differentiation of neural floor plate in vertebrates
 B.  responsible for anterior/posterior axis of the limb in vertebrates
 C.  responsible for determination of the dorsal lip in amphibians
 D.  responsible for cell identities within Drosophila segments
 E.  responsible for determination of dorsal/ventral fates in the neural tube
 F.  all of the above are functions of hedgehog (sonic hedgehog)
 

13. (5 points)  Put the following developmental events in their proper order

A.  AER secretes FGF8
B.  intermediate mesoderm secretes FGF8
C.  FGF8 induces proliferation of mesodermal limb bud cells
D.  AER is determined by overlap in FGF and radical fringe expression
E.  mesodermal cells stop proliferating and express a proximal/distal pattern of HOX genes
F.  HOX gene expression determines the position of the limb
 
 

14.  (5 points)  In laboratory we used a lac Z reporter gene construct to look at expression of the ftz pair rule gene in Drosophila.  If we had a reporter gene construct attached to the promoter of the radical fringe gene in a frog embryo,  where would we expect to see beta-galactosidase activity?  What factors might we expect to affect transcription of this construct?
 
 

15.  (10 points)  Transplantation experiments have been very useful in understanding the develop-ment of the limb.  Below are descriptions of some of these types of experiments.  For two of the three of these experiments, give a brief explanation or diagram of the outcome of the trans-plantation experiment and a brief summary of the conclusions one can make from the experiment.

A.  The AER (apical ectodermal ridge) from a limb bud is transplanted next to the native AER of a limb bud, in other words two AERs now are side by side.
 
 

B.  Mesodermal limb precursors of a forelimb are removed and replaced by the mesodermal precursors of a hindlimb.
 
 

C.  The Zone of Polarizing Activity (ZPA) of one limb bud is transplanted to the anterior of another limb bud so that this limb bud now has two ZPAs.
 
 

16. (15 points)  A.  Define the following terms and briefly describe an example of each from this semester of Developmental Biology:
 

differentiation
determination
induction
pattern formation
regulative development
 

17.  (10 points)  Answer either question A or B from the comprehensive discussion list.

A.  What are the evolutionary connections between the development of all organisms?  How does form and structure evolve through development?  Why is the field of development becoming central to the field of evolution?

B.  What is morphogenesis? How does it differ from determination and differentiation?  Describe in detail a process that involves morphogenesis including a physical description of the process and the molecules involved.