DNA replication and division in binary fission

Steps:

• Cell V is pre-replication (G1 phase): 1 unit DNA.
• Cell W post-replication (S/G2 phase): 2 units DNA.
• Cell X during mitosis: 2 units as duplicated chromosomes align and separate.
• Cells Y and Z after cytokinesis: each 1 unit DNA.

Why C is correct:

• Sequence 1 2 2 1 1 aligns with binary fission, where DNA doubles in S phase and stays doubled through mitosis until division halves it per cell.

Why the others are wrong:

• A: Delays replication until after division, violating cell cycle order.
• B: Halves DNA prematurely during mitosis, but total DNA remains 2 until cytokinesis.
• D: Starts with excess DNA (2 units), inconsistent with a standard haploid starting cell.

Final answer: C