All About Mutations
Part 3

What it means to have a mutation and what role mutations play in Huntington’s disease.

How do expansions occur?

This question has been the subject of a great deal of scientific research over the years. Although the exact cause is uncertain, two phenomena, unequal crossing over and polymerase slippage, are the most probable mechanisms for expansion of the CAG codon.

Below we discuss two proposed models:

• The Unequal Crossing Over Model
• The Polymerase Slippage Model

Last Modified: 1-28-04

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