Cell Cycle

Question.

199. The correct sequence of cell cycle is:

1. G0-G1-S-G2-M.

2 .G0-G1-G2-S-M.

3 .G0-M-G2-S-G1.

4 .G0-G1-S-M-G2.

Answer

1. G0-G1-S-G2-M.

Reference

Robbins 6^th Edition Page 50

KDT 4^th Edition Page 836

Quality

Spotter

Status

Repeat

QTDF

Robbins

Discussion

The normal cell cycle proceeds as G1 à S à G2 à M à G1

Some times after M the cels go into a state of rest called G0. Then they come back to G1 ie G0 à G1 à S à G2 à M à G1

And certain drugs act over certain phase

Phase	Drugs
G1	Vinblastine
S	Methotrexate, Cytarabine, 6-TG,6-MP, Hydroxyurea Mitomycin C, Doxorubicin, Daunorubicin
G2	Daunorubicin, Bleomycin, Etoposide
M	Vincristine, Vinblastine, Paclitaxel

Explanation

1. G0-G1-S-G2-M. is the correct sequence

2 .G0-G1-G2-S-M is an incorrect sequence

3 .G0-M-G2-S-G1 is an incorrect sequence

4 .G0-G1-S-M-G2 is an incorrect sequence

Comments

Cell cycle is gaining importance as our understanding of the cyclins and other molecules increase !!

Tips

If you feel that your memory is failing you often remember that the most sensitive phase to Radiotherapy is G2M That means G2 is followed by M. We know that two G won’t come next to each other. Hence only S can come before G2 and…. so on ……