Chapter 18, Problem 9P

Suppose that you generated flies containing a transgene (sev-Ras^S17N</I>) that uses wild-type sevenless regulatory sequences to drive the expression of coding sequences encoding a dominant negative form of the Ras protein.

a.	Would you expect these flies to have a mutant phenotype? Explain.
b.	Suppose you used these transgenic flies in a modifier screen. For each protein in Fig. 18.6 (p. 604) state whether loss-of-function mutations in the corresponding gene could have been identified as enhancers or suppressors of the mutant phenotype.
c.	Answer part (b) if the flies contained a sev-RasG12V (hypermorphic Ras) transgene instead.