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Regulation of the Lactase Gene

Possible Mechanisms for Lactase Persistence

There are many possible explanations for how this type of mutation works. For example, (a) the mutation causes the activator molecules to bind more strongly to the enhancer region or (b) the mutation causes the repressor molecules to no longer bind to the enhancer region.

A diagram depicting mutations that can either cause increased activation or weakened repression.
The top half of the diagram is marked with the letter A and shows a horizontal double helix with the central portion highlighted. The highlighted portion is labeled Enhancer. Below the highlighted portion is a double ended blue arrow pointing to an irregular bluish mass below it labeled Activator. The word Stronger appears next to the arrow. The lower half of the diagram is marked with the letter B and shows a horizontal double helix with the central portion highlighted. Below the highlighted portion is a red circle with a diagonal slash across the middle. Below the circle is an irregular red mass labeled Repressor. The word Weaker appears next to the circle with the slash.