what controls each phase of a cell cycle? a) Genes...

[marciaabennett]

...b) Enzymes c) DNA d) Mother?

[gileadgirl2008]

Ezymes do definitely, I am doing the osmosis and IPMAT phases in biology right now

[lovely green eyes]

You can't have such simplistic answers. It is just wrong!!

I suppose, even if you HAD to choose one, it would be very difficult to distinguish between a) Genes and b) Enzymes, as it would be similar to the question of whether the egg came before the chicken or vice versa. You need enzymes in order to "transcribe" and "translate" the genes that control the cell cycle progression. On the other hand, the products of these genes could be described as a special class of Enzymes.

Of course we are talking about the CYCLIN DEPENDENT KINASES, which are the motors that drive the passage through the different phases of the cell cycle. Kinases are enzymes, but the activity of these kinases are regulated by the binding of the CYCLIN subunits, which are nornally transcribed de-novo from DNA genes (as they are rapidly degraded and they "cycle")... So you choose!

If you need the complexes working at each cell cycle phase then:
CDK4-CYCLIN D and CDK6-CYCLIN D control the G1-S transition
CDK2-CYCLIN E and CDK2-CYCLIN A control the transition through S phase (activating each replication origin)
and CDK1 (1.e. CDC2)-CYCLIN B control the transition between G2 and M.