Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle? see concept 12.3 (page 244) view available hint(s)

Cells will usually divide if they receive the proper signal at a checkpoint in the G1 phase of the cell cycle. In mammalian cells , this checkpoint is called the restriction point. The G1 phase is a phase of the cell cycle that takes place in eukaryotic cell division. In this phase the cell synthesizes mRNA and proteins in preparation for the subsequent steps leading to mitosis. It ends when the cell moves into the S phase of interphase. 

Ais the answer for you

Giga is the second highest prefix on the normal scale, the first is terra.