What structure pulls chromosomes away from the middle of the cell during anaphase?

• A. Cell membrane
• B. Nuclear envelope
• C. Centrioles
• D. Spindle fibers

Answer: (D)

Verified step by step guidance

1. Understand the context: Anaphase is a stage in mitosis where replicated chromosomes are separated and moved to opposite poles of the cell.
2. Identify the key players: During anaphase, the structures involved in moving the chromosomes are the spindle fibers, which are part of the mitotic spindle apparatus.
3. Recognize the role of spindle fibers: Spindle fibers are composed of microtubules that extend from the centrioles located at opposite poles of the cell.
4. Explain the mechanism: The spindle fibers attach to the centromeres of the chromosomes and shorten, pulling the sister chromatids apart toward the centrioles.
5. Clarify the function of other structures: The cell membrane and nuclear envelope do not play a direct role in pulling chromosomes apart during anaphase; their roles are more structural and regulatory in the cell cycle.