Types of mutations and their impact on protein function Today's ...
Types of mutations and their impact on protein function Today's ...
Types of mutations and their impact on protein function Today's ...
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Another example <str<strong>on</strong>g>of</str<strong>on</strong>g> a recessive loss-<str<strong>on</strong>g>of</str<strong>on</strong>g> functi<strong>on</strong> allele:<br />
Lactose intolerance is usually the result <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
“reducti<strong>on</strong>-<str<strong>on</strong>g>of</str<strong>on</strong>g>-functi<strong>on</strong>” alleles that<br />
have low expressi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> the lactase enzyme in adults<br />
disaccharide m<strong>on</strong>osaccharides<br />
Lactose tolerance (also known as persistence) is, historically speaking, the “mutant” form.<br />
Most mammals (including early humans) do not drink milk after infancy, <str<strong>on</strong>g>and</str<strong>on</strong>g> the lactose<br />
gene is usually inactivated (i.e., shut <str<strong>on</strong>g>of</str<strong>on</strong>g>f). Many human populati<strong>on</strong>s, particularly in Europe,<br />
where dairy cows were domesticated, acquired the ability to metabolize lactose<br />
throughout adult life, most likely by mutati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> regulatory elements in the lactase gene<br />
promoter regi<strong>on</strong>.<br />
This has apparently happened independently am<strong>on</strong>g some east African populati<strong>on</strong>s.<br />
Lactose intolerance is very prevalent am<strong>on</strong>g n<strong>on</strong>-European populati<strong>on</strong>s.<br />
Lactose tolerance is dominant over intolerance, for reas<strong>on</strong>s that should be obvious. In<br />
other words, lactose intolerance shows recessive inheritance.<br />
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