Answer to Question #44980 in Molecular Biology for lee min
Which option about cell cycle checkpoint is correct?
a) the decision to cross the R point is irreversible
b) some decisions made at checkpoints are reversible
c) all decisions made at checkpoints are reversible
d) option a & b
e) option a & c
There are five major transitions between sequential stages of the cell cycle in eukaryotes:
G1a/G1b - the ‘restriction or R point’ in mammalian cells, ‘Start’ in yeast;
G1/S - initiation of DNA synthesis;
G2/M - entry into mitosis;
metaphase/anaphase - chromosome alignment on the mitotic spindle;
telophase/G1 - exit from mitosis and return to G1 phase.
Progression through each of these transitions is irreversible. Thus, the correct answer is a) the decision to cross the R point is irreversible