Lactase Persistence: Biology and Evolution Flashcards
What is lactase persistence?
The ability to digest lactose into adulthood due to continued lactase enzyme production.
What gene is responsible for lactase production?
The LCT gene on chromosome 2.
What type of mutation leads to lactase persistence?
A regulatory mutation (C → T SNP) in the MCM6 gene.
What is the main function of lactase?
To break down lactose into glucose and galactose.
What populations show the highest lactase persistence?
Northern Europeans, East African pastoralists, and some South Asians.
How does lactase persistence provide a survival advantage?
It allows adults to consume milk as a source of calories, hydration, and nutrients.
What is a selective sweep?
A reduction in genetic diversity around a beneficial allele due to strong positive selection.
How does linkage disequilibrium relate to lactase persistence?
SNPs near the lactase gene are inherited together, forming patterns of linkage disequilibrium.
What is co-evolution of genes and culture?
The interaction where cultural practices, like dairying, influence genetic selection.
Name an example of convergent evolution in lactase persistence.
Independent mutations in Europe and Africa leading to the same trait.
Why is lactase persistence considered a dominant trait?
Because the persistence allele is expressed and produces lactase even when only one copy is present.
What happens at the molecular level in heterozygous individuals for lactase persistence?
One allele produces lactase while the other does not; transcription and translation of the persistence allele create the enzyme.
How does lactase persistence vary in individuals with different genotypes?
Homozygous for persistence: High enzyme levels.
Heterozygous: Moderate enzyme levels.
Homozygous for non-persistence: No lactase production
What is the enzymatic role of lactase?
It breaks down lactose into glucose and galactose, allowing digestion of milk.
What evidence supports lactase persistence as recent human evolution?
Tishkoff et al. (2007) showed that lactase persistence alleles arose within the last 10,000 years in dairying populations.
