# Explain how the spindle apparatus ensures the accurate distribution of chromosomes to daughter cells during mitosis.

> IB DP Biology Standard Level (2023 syllabus) — D2.1 Cell and nuclear division · Explain · 4 marks

## Mark scheme (4 marks)

1. Spindle fibres (microtubules) attach to chromosomes at the centromere / kinetochore during prometaphase/metaphase.
2. Each sister chromatid of a chromosome is attached to spindle fibres from opposite poles, ensuring chromosomes align at the metaphase plate / equator.
3. During anaphase, spindle fibres shorten/contract, pulling sister chromatids apart to opposite poles.
4. This ensures each daughter cell receives one copy of each chromosome (the correct/same chromosome number as the parent cell), maintaining genetic continuity.

## Key terms

- [spindle apparatus](https://www.gradenine.co.uk/glossary/spindle-apparatus)

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-spindle-apparatus-ensures-13c5873d) · Published by Druglandscape Ltd.