29.1: Introduction
- Page ID
- 148600
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Figure \(\PageIndex{1}\): Finnish families with lactase non-persistence (hypolactasia). Filled symbols represent biochemically verified hypolactasic individuals with non-persistence; asterisks indicate that no sample was available; question marks represent unknown affection status and arrows and numbers indicate the individuals whose DNA was used for sequencing (Enattah, N., Sahi, T., Savilahti, E. et al. Identification of a variant associated with adult-type hypolactasia. Nat Genet 30, 233–237 (2002). https://doi.org/10.1038/ng826)
A pedigree is a diagram or chart that shows the genetic history and relationships within a family over multiple generations.
Pedigrees played a crucial role in determining the inheritance pattern of lactose intolerance. Scientists analyzed family pedigrees to observe how the trait was passed down through generations. By studying these pedigrees, researchers noticed that two lactose-tolerant parents could have lactose-intolerant children, indicating that the trait was recessive. The occurrence of the trait in both males and females suggested it was not X-linked. Multiple pedigrees were examined to increase confidence in the findings, as a single pedigree would not provide sufficient evidence. These pedigree analyses consistently supported the conclusion that lactose intolerance is inherited as an autosomal recessive trait. The use of pedigrees, combined with genetic analysis, allowed scientists to establish that lactose tolerance (lactase persistence) is autosomal dominant, while lactose intolerance is autosomal recessive.