Final answer:
An individual with a functional lactose gene retains the ability to digest lactose regardless of thirst level, but overall metabolic functions could be affected by severe dehydration. Lactose intolerance, in contrast, results from a lack of sufficient lactase enzyme, leading to digestive problems when consuming lactose-containing products.
Step-by-step explanation:
The ability to digest lactose in adults is primarily influenced by the presence of the enzyme lactase, which breaks down lactose into glucose and galactose. If an individual who has a functional lactose gene is dying of thirst, their ability to digest lactose would remain unaffected. However, dehydration could impair the individual’s overall metabolic functions, possibly hindering their ability to carry out other chemical reactions efficiently, including those not related to lactose digestion.
Lactose intolerance is a condition where individuals lack sufficient lactase, resulting in the inability to digest lactose properly. This can cause gastrointestinal symptoms such as bloating, cramps, and nausea. People with lactose intolerance must manage their condition by consuming lactose-free products or taking lactase supplements.
Regarding evolutionary aspects, the ability to digest lactose into adulthood, known as lactase persistence, is thought to have offered a nutritional advantage in certain populations. This has influenced cultural practices, such as dairy farming, and has been an essential factor in human adaptation and evolution.