Talk:Lactose intolerance

Students are developing this article as part of an Eduzendium course.

Just a note about bolding the title phrase. We only bold the title of the article the first time it is mentioned in the article, not each time. The article looks to be coming together nicely! :) David E. Volk 16:42, 14 March 2008 (CDT)

Genetics

This opening part of the genetic section seems a little confused.

Lactose intolerance is an autosomal recessive trait. Lactase is produced if one or two of the two genes that code for it are present. The dominant allele codes for both of these genes, and therefore the reduction of lactase synthesis. It is likely that selection was a main factor in determining the distribution of lactose intolerance.

A few points:

• I think that lactase is produced by all the alleles the difference is the temporal and spatial aspect of expression. i.e put simply either early only (intolerance) or late (persistance).
• An allele cannot code for a gene. It is a variant of a gene.
• The dominant allele of the gene expresses late and therefore would not be regarded as a reduction of lactase synthesis.
• Selection was for the dominant allele not the recessive allele. The recessive allele (ancestral) has the lactose intolerance phenotype (lactase expressed early only). A mutation occurs in the regulatory region that results in the lactase gene being expressed later in development and results in the lactase persistent phenotype. This is an advantage in milk drinking cultures and thus the dominant allele predominates in cultures dominanted by dairy products.

I hope this is useful for you. Chris Day 23:47, 15 April 2008 (CDT)