One cells takes 80 minutes to form 16 cells. If 2 cells undergoes division simultaneously, it take 160 minutes (2 hours 40 minutes) to form 32 cells.

The first gap phase - 2C amount of DNA in cells of G₁. The cells become metabolically active and grows by producing proteins, lipids, carbohydrates and cell organelles including mitochondria and endoplasmic reticulum. Many checkpoints control the cell cycle. The checkpoint called the restriction point at the end of G₁, determines a cells fate whether it will continue in the cell cycle and divide or enter a stage called Go as a quiescent stage and probably as specified cell or die. Cells are arrested in G₁ due to:
(i) Nutrient deprivation.
(ii) Lack of growth factors or density dependent inhibition.
(iii) Undergo metabolic changes and enter into G_o state.
Biochemicals inside cells activates the cell division. The proteins called kinases and cyclins activate genes and their proteins to perform cell division. Cyclins act as major checkpoint which operates in G₁ to determine whether or not a cell divides.

The replication of chromosomes in the absence of nuclear division and cytoplasmic division resulting in numerous copies within each cell is called endomitosis. Eg: Polytene chromosome.

Significance of meiosis:
1. This maintains a definite constant number of Chromosomes in organisms.
2. Crossing over takes place and exchange of genetic material leads to variations among species. These variations are the raw materials to evolution. Meiosis provides genetic variability by partitioning different combinations of genes into gametes through independent assortment.
3. Adaptation of organisms to various environmental stress.