Styling, of hair

The a-keratin of hair is rich in the amino acid cysteine. The location of these cysteines in the protein chain is genetically determined as a result of the location of the cysteines in the protein, a person may have curly, wavy, or straight hair. How can the location of cysteines in a-keratin result in these different styles of hair Propose a hypothesis to explain how a "perm" causes straight hair to become curly. 

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