Question

consider what happens in each part of the cell cycle. why does dna replication have to occur before mitosis, in interphase? mitosis sends one copy of each chromosome to each daughter cell, so it cant occur unless replication has already made the copies. mitosis is the same as saying cell division, and the physical separation that divides cells depends on dna replication. mitosis is the same as saying chromosome replication—they are the same thing.

Explanation:

• First option: Mitosis distributes one copy of each chromosome to daughter cells. Without prior DNA replication (in interphase) to make copies, there would be no extra set to send. This is correct as per cell - cycle mechanics.
• Second option: Mitosis is not just cell division (cytokinesis is the physical separation part). Also, the physical separation (cytokinesis) is not directly dependent on DNA replication in the way described. DNA replication is for genetic content, not the physical act of cell splitting.
• Third option: Mitosis is the process of nuclear division (and subsequent cell division in some cases). Chromosome replication occurs in interphase (S - phase). They are not the same.

Answer:

First option: Mitosis sends one copy of each chromosome to each daughter cell, so it can't occur unless replication has already made the copies.