Tag Archives: PKU

Four steps to interpret and move beyond nature-nurture (for a handbook on environmental studies)

My four steps to interpret and move beyond nature-nurture for the current draft of a 1500-word entry for a handbook on environmental studies: Continue reading

PKU: Heritability, changeability, and gene-environment interaction

PKU (Phenylketonuria) is a condition that is often invoked to demonstrate that genetic does not mean unchangeable. It is also often cited as a trait with 100% heritability in normal environments that can, nevertheless, be changed and in the right environment have zero heritability. This post explains why these two sentences are not synonymous and how the second is flawed and reinforces an incorrect idea of heritability. I also examine PKU in terms of measured genetic and environmental factors, arriving at the counter-intuitive idea that no gene x environment interaction is involved. Continue reading

50 whys to look for genes: 30. Genetic heterogeneity

Genetic heterogeneity refers to

either: a) a multiplicity of mutations within some gene and a spectrum of corresponding values for a trait (or “phenotype”), each of which varies little within the typical range of locations (i.e., allelic heterogeneity); or b) the trait exists if any one of a range of loci has the atypical form (i.e., locus heterogeneity).

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50 whys to look for genes: 13. Genetics is “the future of medicine”

[A] deeper understanding of the fundamental mechanisms of life promises to lead to an era of molecular medicine, with precise new ways to prevent, diagnose, and treat disease.  National Human Genome Research Institute report, Genetics: The Future of Medicine.

(Google “genetics promise medical treatment” and many similarly confident statements can be found.)

Phenylketonuria (PKU) is the poster child for genetic medicine. Continue reading

50 whys to look for genes: 1. Understand how the living world operates (at molecular level)

One reason to look for the genetic basis for an observed trait is to understand how the living world operates at molecular level.

Complication
A complication is evident in the case of phenylketonuria (PKU) in humans.  PKU has been shown to be associated with having two copies of a malfunctioning gene for the enzyme phenylalanine hydroxylase (PAH). The cognitive development of such individuals is extremely impaired by the level of phenylalanine present in normal diets.  However, the detection of PKU in newborns is possible on the basis of a biochemical test, which was widely applied before the genetic basis was known.  Biochemical, not genetic screening, continues to be the basis for initiating the diet needed to prevent the cognitive impairment that had been associated with PKU.  The more general issue is, if we want to understand how the living world operates at molecular level, when do we need to go beyond the biochemistry to look for the genes?

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(Introduction to this series of posts)

Diagramming Intersecting Processes (a 30-minute guest activity for a class on graphic organizers)

Diagramming Intersecting Processes

Preamble on my motivation: I want more people to think in terms of “intersecting processes” (Taylor 2001), which means being able to read the diagrams I present, appreciate the theoretical implications of the concept, start to make their own accounts and diagrammatic depictions, and teach others to do the same.

Goals for students: 1. to understand the development of biomedical and social phenomena in terms of linkages among processes of different kinds and scales that build up over time—genetics, treatment, family and immediate social context, social welfare systems and economics, wider cultural shifts, ….
2. to use graphic organizers to help them visualize such “intersecting processes” and to identify places where detail is missing and where further inquiry is needed. Continue reading

“What Europe can learn from the World?”

My first, mostly unscripted take of a response to an invitation to prepare a very short video where Activists and Scholars respond to the question: “What can Europe learn from the World?” http://www.youtube.com/embed/9Jn0GMweuTs I shift the question to what can European researchers learn.

Takes 2 or 3 or… are needed.  My video is far longer than the others on the current playlist: http://www.youtube.com/playlist?list=PLXGOQzlnH7jRLCQoyqIpubpBcz-FSVie8