Question

7. You perform the following microscopy experiments to measure the signaling output of two pathways and observe the following results. Experiment 1 - You genetically tag an M-cyclin with GFP. You add an upstream signal to a cell culture to activate the M-cyclin. Result 1 - GFP fluorescence intensity increases. Experiment 2- You genetically tag adenylyl cyclase with RFP. You add an upstreanm signal to a cell culture to activate adenylyl cyclase. Result 2 There is no change in the RFP fluorescence intensity. A. (4pts) Why would adding the respective upstream signals lead to changes in Cyclin A-GFP intensity but not adenylyl cyclase-RFP intensity? B. (4pts) For experiment 1, predict the timescale over which the GFP intensity increases Extra Credit (2pts) An article by Casas-Selves and DeGregori in the joumal Evolution states, "Cancer development within an individual is also an evolution ary process..." Please provide a short reflection (3 sentences max) on why this statement is an accurate description of how most cancers progress

Answer 1

​​​​​​​Answer 4A)

• In case of M-cyclins, they control of process of regulating the mitotic phase of cell cycle.
• It works by initiating this mechanism allowing spindle assembly and chromatid alignment.
• When an upstream signal is acting upon this protein, there is a direct integration of the signal enhancing the levels. This is positive regulation. To tag this, GFP or green Fluorescent Protein is used.  
• In terms of adenylyl cyclase tagged with RFP, problems can arise in one of the two ways.
  1. ​​​​​​​​​​​​​​The RFP can take longer time to generate Fluorescence as compared to GFP. This can lead to error in tagging expression.
  2. But as stated above, there is no increase in expression and can reflect the fact that Red Fluorescent Protein can interacts with the protein altering the expression.
• Apart from this, Adenylyl cyclase is not the target upstream sequence. The interaction is always G-protein mediated. So, this can be the reason why the upstream signal may have not been able to stimulated the downstream Adenylyl cyclase.