Answer to Question #93385 in Biochemistry for Kylie

Question

Describe lactose intolerance.

Answer 1

Lactose intolerance is a disease caused by lactase deficiency. Lactase is an enzyme which breaks down milk sugar lactose into glucose and galactose. Lactose moves through digestive system of lactose intolerant person, interacts with bacteria and in result of fermentation causes such symptoms as diarrhea, nausea, abdominal cramps, bloating, gas.

Lactose intolerance can be caused by genetic or environmentally induced factors. Talking about genetic factors, 2 genes are involved: LCT – responsible for making lactase, MCM6 – controls LCT (switches LCT off or on, depending on presence of lactose). Both genes are located on the long arm (q) of chromosome 2 in region 21. As a result of evolution human developed mutation in MCM6 gene which is consistently turned on (allowing lactase to metabolize lactose) during the lifetime of a person (not only at breastfeeding phase like our ancestors had). Lactose intolerant people lack this mutation so MCM6 gene turns off LCT after breastfeeding is stopped. Environmentally induced factors or epigenetic factors are accumulated during a lifespan, they can cause lactose intolerance in elderly individuals. Such epigenetic factor is DNA methylation in the LCT and MCM6 gene which result in lower production of lactase enzyme.