---
title: "Microtubules, Dynamic Instability and the Spindle"
description: "Microtubules grow and shrink in sudden switches rather than smoothly, which lets them search space until an end is captured and held. That search is how a spindle finds every chromosome."
canonical: https://lightmysky.com/learn/science/microtubules-dynamic-instability-and-the-spindle-mt_RWhMJxOmUu
source: https://lightmysky.com/learn/science/microtubules-dynamic-instability-and-the-spindle-mt_RWhMJxOmUu.md
retrieved: 2026-09-12
---

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# Microtubules, Dynamic Instability and the Spindle

Microtubules grow and shrink in sudden switches rather than smoothly, which lets them search space until an end is captured and held. That search is how a spindle finds every chromosome.

Subject: Science · Area: Organisms & Life Processes · Ages 20 to 22
Page: https://lightmysky.com/learn/science/microtubules-dynamic-instability-and-the-spindle-mt_RWhMJxOmUu

## Ready when they can

- Describes dynamic instability as switching between growth and rapid shrinking, and says what triggers the switch.
- Explains how search and capture attaches a spindle fibre to a chromosome without aiming.
- Predicts what a drug that freezes microtubules does to a dividing cell.

## Lesson: How the spindle finds every chromosome

Microtubules do not grow smoothly. Each one switches between steady growth and rapid shrinking. A change at the growing tip flips the switch from one mode to the other.

The spindle uses this switching to search space. Many microtubules grow outward in all directions, shrink back, and grow again. The end that bumps into a chromosome is captured and held.

**Example.** Picture the spindle casting out lines again and again with no aiming. Most lines miss and shrink away. The few that touch a chromosome lock on, until every chromosome is held.

**Tip.** A drug that freezes microtubules stops the whole search. With no growing and shrinking, no new attachments form, and the dividing cell stalls.

**Recap.** Switching ends search blindly, capture holds the hits, and freezing breaks division.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Actin Filaments: Polarity, Treadmilling and Cell Shape](https://lightmysky.com/learn/science/actin-filaments-polarity-treadmilling-and-cell-shape-mt_sJlYoA-BnA)

## Opens up

- [Motor Proteins and Directed Movement Along Tracks](https://lightmysky.com/learn/science/motor-proteins-and-directed-movement-along-tracks-mt_TUTmILr7y0)