The fruit fly has 8 chromosomes (2n) in each cell. During the interphase of Mitosis if the number of chromosomes at the G₁ phase is 8, what would be the number of chromosomes after the S phase?

Concept:

• In eukaryotic cells, the cell cycle is divided into two phases; the interphase and the M phase.
• The M phase refers to mitotic division while the interphase is the duration between two successive mitosis divisions.

Explanation:

• Interphase 
  • It is the time during which a cell is preparing for its division by undergoing cell growth and DNA replication.
  • There are three phases in interphase: G1 phase, S phase, and G2 phase.

• Sl. No	Phase	Key event
  1	G1 phase	It is the time period between mitosis and DNA replication.  During this phase, the cell is metabolically active and continues to grow. There is no DNA replication in this phase.
  2	S phase	It is called the synthesis phase. During this process, DNA replication occurs, and the amount of DNA in the cell doubles. However, the chromosome number in the cell remains the same.
  3	G2 phase	In this phase protein synthesis occurs to prepare the cell for mitosis division and the cell continues to grow.

   

• It is given that the number of chromosomes in the G₁ phase in fruitfly = 8.

• To find the number of chromosomes after the S phase.

• Since the number of chromosomes doesn't change after the S phase, the number of chromosomes in the fruitfly after the S phase will be 8.

So, the correct answer is option 2.