Magic genes

The magic gene is a portion of human that determines whether a person will have magical abilities. Those people born with the gene active are witches and wizards, while those who are not are Muggles or Squibs.

The magic gene is dominant, and any child born to a wizarding family will have some degree of magical ability, or at least magical awareness. Squibs, while unable to use magic, are still able to function within the wizarding world to a limited degree. The descendants of squibs who instead integrate into the Muggle world and marry will usually be Muggles, although the magic gene occasionally resurfaces in later generations and produces a Muggle-born witch or wizard.

Behind the scenes

 * J.K. Rowling stated that she had considered having Dudley Dursley have a magical child in the epilogue, and see them off to Hogwarts at Platform 9&frac34; at the same time as Harry and his family. She decided against this, however, stating that any latent wizarding genes would never survive contact with Uncle Vernon's DNA.
 * According to J.K. Rowling, nobody knows where magic comes from.
 * Despite the magic gene being dominant, that doesn't explain Squibs or Muggle-borns, or how muggle borns manifest their powers the same way as Half-bloods or Pure-bloods. It is therefore possible that magic is controlled by more than one gene or is only partially dominant.

Appearances

 * Harry Potter and the Half-Blood Prince
 * J. K. Rowling Official Site