pulse-chase experiment

BIO 353 Homework Assignment #3

This assignment is to be completed by each student without aid from other students (i.e. sharing of assignments or drafts of assignments between students is not acceptable). Also the assignment is to be completed without accessing the original paper from the literature. Safe Assign with check your work for similarity to both the work of other students and to the original text of the paper assigned.

Please submit the assignment as one document. Your name (first and last) and your ID number should be on each page. Total points available for assignment #3 = 34 points.

Homework Assignment #3 (electronic version) is due on Monday, November 19^th by NOON. Please submit the electronic version of your assignment via the link in the assignments folder on blackboard. This electronic version will contain parts A,B,D and E but not part C. Late electronic versions will not be accepted and the student will automatically forfeit 15 points for not electronically submitting. PLAN AHEAD! A hardcopy version including ALL parts (A-E) is due on the same day IN CLASS. Hard copy assignments must be handed to one of the TAs. (The lecturer, Dr. Ugarova, will not collect or be responsible for any homework assignments). Persons unable to be in class that day should plan on delivering their hard copy to a TA prior to this due day. Late hardcopy assignments (submitted to one of the TAs) will be reduced 10% in grade for each day they are late and will not be accepted if more than 2 days late. This policy will be strictly enforced on this round! PLAN AHEAD!

The questions and activities for the third homework assignment are as follows:

(7 pts) In your own words explain what is meant by a pulse-chase experiment? Next, explain why a “pulse-chase” experiment might give results that are easier to interpret than an experiment in which radioactive amino acids are added but never washed away?

(5 pts) During the pulse-chase experiment, rabbit parotid tissue needed to be incubated in a buffer in a flask. If you were carrying out this experiment what characteristics of the buffer would be critical in keeping the tissue alive and functioning well over a several hour period? Identify at least five.

(8 pts) Using the data in Table 3 of the paper, prepare a graph that illustrates this data and which could be used as Figure 13 in the paper. You are allowed to omit the data for nuclei and mitochondria in this graph. You are also allowed to sum up the “Golgi periphery/entrance cisternae” and “Golgi exit/condensing cisternae” data at each time point and use these summed numbers to plot a “Golgi Total” curve if you wish. Be sure to include a figure title, axis titles and a symbol legend. Beside each data point put its magnitude. The figure MUST be drawn by hand and NOT by a graph preparing program like Excel! Photocopies will NOT BE ACCEPTED! Note that the drawing should not be submitted electronically to Safe Assign but the other parts of this homework must be. The entire assignment including this original drawing must be submitted in class. To be safe please make a photocopy of your graph that you retain for backup purposes only.

(7 pts) Write a figure legend for the figure you have prepared which summarizes the autoradiographic data supporting the existence of a secretory pathway. You should use a maximum of 100 words.

(7 pts) The parotid salivary gland can be stimulated to secrete its proteins by exocytosis using the drug isoproterenol (a mimic of the neurotransmitter norepinephrine). Describe an experiment these authors might develop to measure protein secretion from this tissue into the extracellular space.