DNA Molecules Double After Replication in Mitosis

Steps:

• Muscle cells start with 64 chromosomes, each with 1 DNA molecule in G1 phase (64 total DNA molecules).
• S phase replication doubles DNA, creating 64 chromosomes with 2 sister chromatids each (128 DNA molecules total).
• Early prophase occurs post-replication; condensed chromosomes have 128 DNA molecules.
• Telophase follows chromatid separation to poles, but the undivided cell retains both sets (128 DNA molecules).

Why C is correct:

• Mitotic cells maintain 4C DNA content (128 molecules for 2n=64) from prophase to telophase, per cell cycle definitions.

Why the others are wrong:

• A: Ignores replication (64 in prophase) and confuses chromatid separation with DNA loss (32 in telophase).
• B: Treats prophase as pre-replication (64) and incorrectly halves DNA in telophase before cytokinesis.
• D: Correct for prophase (128) but assumes telophase reduces DNA to 2C prematurely in one cell.

Final answer: C