G1 phase

Cell Biology.
  1. the first growth period of the cell cycle, during interphase, in which the cell grows and cytoplasmic organelles are replicated.

Origin of G1 phase

G abbreviation for growth

G2 phase

Cell Biology.
  1. the second growth period of the cell cycle, following DNA replication and preceding prophase, during which the cell forms the materials that make up the spindle.

Origin of G2 phase

1970–75; G abbreviation for growth
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018