Experimental theory

[salemstein]

I just want to get a better understanding in general when dealing with these types of questions. Say you're trying to prove increasing "A" causes an increase in "B". "A" is moderately expressed in WT/natural conditions. Which would better prove my case:
Scenario A: I run an experiment where A is increased. Results show B increased 50%.
Scenario B: I run an experiment where an antagonist of A is increased. Results show B decreased 50%.

---

Members don't see this ad.

 

[aldol16]

They would both prove your case, although two aspects of it. When scientists think of "proving" that something causes something else, we think of two criteria: necessity and sufficiency. These are extremely important. Necessity means that A is necessary in order for B to occur. To test this, you would block A and see if B is blocked as well - if it is, you can say that A is necessary for B. Sufficiency means that A is sufficient for B to occur. To test this, you would upregulate A and see if that is sufficient for upregulation of B - if so, you can say that A is sufficient for B.

 

[salemstein]

They would both prove your case, although two aspects of it. When scientists think of "proving" that something causes something else, we think of two criteria: necessity and sufficiency. These are extremely important. Necessity means that A is necessary in order for B to occur. To test this, you would block A and see if B is blocked as well - if it is, you can say that A is necessary for B. Sufficiency means that A is sufficient for B to occur. To test this, you would upregulate A and see if that is sufficient for upregulation of B - if so, you can say that A is sufficient for B.

But assuming you keep everything else the same, if upregulating A led to an increase in B, wouldn't that show that A is necessary for B to increase?

 

[aldol16]

But assuming you keep everything else the same, if upregulating A led to an increase in B, wouldn't that show that A is necessary for B to increase?

No because B could still increase without A. Several possible alternatives could exist. For example, say B is downstream of both A and C in parallel pathways such that A is not necessary for B to increase as long as C is there. Look up "necessity and sufficiency" on Google and that should yield you some good explanations.