Tag Archives: heterogeneity

http://sicw.wikispaces.umb.edu/heterogeneities

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

What to do if we think that researchers have overlooked a significant issue for 100 years?

Practice run of a talk to philosophers of biology & biologists, March 2016 Continue reading

The conflation of family and population helps explain why the Nature vs. Nurture formulation persists II (revised)

Revised version

The first installment ended on the following note: Suppose you have many sets of same-sex non-identical twins raised together and many sets of same-sex identical twins raised together and find that the identical twins are on average more similar.  It seems reasonable to conclude that is because they share all their genes whereas the non-identical twins share fewer of their genes.  Reasonable, but not certain, at least not certain that it is only about genes.  After all, the treatment of identical twins could be more similar than the treatment of non-identical twins, even same-sex non-identical twins.  In any case, that conclusion doesn’t say that it’s the same nature—the same genes—or the same nurture that brings about the resemblance from one pair of twins to the next.  Given this possibility of underlying heterogeneity where are you?  What can you do? 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: 10. Identify risk factors (using GWA studies)

If presence of a section of DNA (SNP) increases the odds of a disease, then look for genes close to the SNP, investigate the enzymes associated with the gene and use that as an entry point to investigation of the etiology of the disease, then try to design drug therapies to counteract any undesired function of those enzymes or their subsequent effects. Continue reading

Troubled by Heterogeneity?: A simple example to illustrate why we might or might not be

Fresh perspectives on modern understandings of heredity and development over the life course can be opened up by examining the ways that research and application of resulting knowledge address—or suppress—heterogeneity in a range of senses (including individual particularity and variation around a mean).  Let me illustrate why we might or might not be troubled by heterogeneity through a personal story that involves the simplest sense of heterogeneity, namely, a group made up of two distinguishable subgroups.

At my annual physical when I turned 50 my doctor recommended a regimen of half an aspirin a day to help prevent a stroke or heart attack.  Not long afterwards I learned that some fraction of the population is resistant to aspirin—it does not produce the desired anti-platelet effect.  This subgroup is, however, still subject to aspirin resulting in an increased risk of serious gastrointestinal bleeding.  Could I find out if I was in the resistant fraction?  My doctor informed me that health insurance companies do not consider testing to be a justified expense for healthy subjects.  It was, he advised, up to me to decide whether to take the daily aspirin.  Some Internet follow-up on my part revealed that testing for resistance is possible, but is undertaken only when patients under treatment for a cardiovascular attack do not seem to be showing the anti-platelet effects of aspirin intake.  Would I devote energy to find others with similar concerns about their aspirin-resistance status and agitate for access to testing?  No—I went along with the health insurance company’s determination and followed the doctor’s advice to make a personal choice, in this case, not to take the daily pill.

With hindsight, my decision was a good one—recent research indicates that in all healthy subjects the decreased average risk of a cardiovascular event might not outweigh the increased average risk of gastrointestinal bleeding (Seshasai et al. 2012).  Yet, these newer findings aside, consider my experience at the time.  In the doctor’s initial recommendation, aspirin-resistant and normal subgroups were treated as a single group of over-50s, all of us subject to the same positive trade-off between cardiovascular and gastrointestinal risks.  The doctor could have been troubled by the heterogeneity within this group, especially after I raised my concerns.  Instead he invoked the rhetoric of patient choice and the constraints of the health insurance system.  I entertained the possibility of joining with others to agitate for testing to determine which subgroup we belonged to.  In the end, I complied with my doctor’s framing of my position, namely, I should see myself as a member of an over-50s group subject to a degree of uncertainty about the positive trade-off.

In this story we can see the three parts of a broad contention—

•  Research and application of resulting knowledge are untroubled by heterogeneity to the extent that populations are well controlled—As the story conveys, I did not comply with my doctor’s initial recommendation, but accepted his subsequent advice.

•  Such control can be established and maintained, however, only with considerable effort or social infrastructure—The authority of medical professionals was not sufficient to achieve my compliance, but the rhetoric of patient choice and the reimbursement guidelines of the health insurance system eventually were.

•  The interplay of heterogeneity, control, and social infrastructure provides an opening to give more attention to possibilities for participation instead of control of human subjects—The Internet gave me a means to go beyond the consultation with my doctor.  It would have been my first port of call if I had embarked on a journey of finding whom to collaborate with to agitate for change in the guidelines for aspirin-resistance testing.

HetContention

Figure 1. Schema that summarizes the contention in the text.  The contention applies both to the modern understandings of heredity and to interpretations of science in Science and Technology Studies (STS). (Colored text narrates the connection between terms linked by the curves. Zigzag lines indicate a tension or contrast, e.g, populations are harder to control if members of the population are able to participate in ways that draw attention to heterogeneity within the population.)

Nature-Nurture? No! (an overview of a book)

Nature-Nurture? No:  Moving the Sciences of Variation and Heredity Beyond the Gaps

Almost every day we hear that some trait “has a strong genetic basis” or “of course it is a combination of genes and environment, but the hereditary component is sizeable.” To say No to Nature-Nurture is to reject this relative weighting of heredity and environment. Continue reading