Mitosis stage and curve identification from cell cycle graph

Steps:

• Recall mitosis stages: prophase (chromosomes condense), metaphase (chromosomes align), anaphase (chromosomes separate), telophase (nuclei reform).
• Identify point X as the transition where sister chromatids begin pulling apart, marking anaphase onset.
• Analyze curve 1: rises during anaphase as spindle fibers shorten and poles move apart.
• Analyze curve 2: falls as chromosomes decondense post-anaphase, indicating completion of separation.

Why A is correct:

• Anaphase begins at X per definition, with curve 1 showing increasing pole separation and curve 2 showing decreasing chromosome tension, matching standard mitotic graphs.

Why the others are wrong:

• B: Metaphase alignment occurs before X; curves reversed from actual separation patterns.
• C: Not enough information (option blank).
• D: Duplicate of B; incorrect stage and curve assignment.

Final answer: A