DNA replication and division in mitosis

Steps:

• Identify cell cycle phases: G1 (2C DNA), S (replication to 4C), G2 (4C), M (division to two 2C cells).
• Plot DNA amount over time: constant in G1/G2, doubles in S, halves post-mitosis.
• Match graph to pattern: rise during S phase, drop after cytokinesis.
• Select graph showing initial plateau, linear increase, second plateau, then sharp decrease.

Why D is correct:

• D depicts DNA doubling during S phase (replication) then halving at mitosis (equitable chromosome segregation per cell theory).

Why the others are wrong:

• A shows constant DNA, ignoring replication.
• B shows steady increase without division drop.
• C shows doubling but no post-mitosis halving.

Final answer: D