A)It regulates Ras signaling through positive feedback control mechanisms.
B)Cells lacking NF1 have higher levels of GTP-bound Ras.
C)NF1 is known as a Ras-GAP.
D)B and C.
E)None of the above.

A)MGMT
B)p16^INK4A
C)PTEN
D)VHL
E)None of the above

A)One inactivating somatic mutation in one copy of Rb.
B)Two somatic inactivating mutations,one in each of the two copies of Rb.
C)One somatic mutation in Rb,leading to its activation.
D)Two somatic mutations in a copy of Rb,leading to its activation.
E)None of the above.