4. (22 pts) You have identified and isolated a
gene that is expressed in differentiated neurons in mice. These
nerves play a role in contractions of eyelid muscles so you name
the gene winky. You join DNA fragments A-H (dark lines
below), normally found upstream of the winky gene, to a
GFP reporter lacking either enhancers or a promoter. The resulting
winky::GFP constructs were introduced into cultured
neuronal cells, and the level of GFP expression was monitored by
looking for green fluorescence.

a. (4 pts) From the results that follow, circle
the region that contains the promoter and the region that contains
a neuronal enhancer? (Label each accordingly.)

b. (4 pts) Justify your answers. Explain how
clones A-H helped you reach each answer.

c. (5 pts) In cultured neuronal cells that
carry a fully functional winky:GFP reporter gene, co-expression of
the shuteye gene leads to very low GFP expression. The
shuteye protein does not have a DNA binding domain yet biochemical
studies show that the shuteye protein associates with histone
deacetylases and a particular lysine methyltransferase. What is the
most likely reason for loss of GFP following expression of the
shuteye gene in these neuronal cells?

d. (3 pts) What is a CpG island ?

e. (3 pts) In which region would you expect to
find a CpG island?

a. adjacent to the translation start
stie

b. near a splice site branch point

c. upstream of the
transcription start site

d. within a transcriptional terminator
loop

e. at the 5´end of a processed
mRNA

f. (3 pts) How might expression of the
shuteye gene affect a CpG island associated with the
winky gene?