Genetic Testing
Introduction
We are rapidly entering the era of personalized genetic testing. However, these tests - usually for markers of diseases including cancer, and estimates of their risks - largely remain unsatisfactory. The concordance of commercial (for-profit) testing available to the consumer, with other assessments of risk (e.g. family histories) is poor, at best. This may reflect - in part - the fact that although "cutting-edge," this technology generally does not account for other factors that affect the expression of our genes, including the mitochondrial genome, and more importantly (I believe): (i) the fact that most diseases are complex phenotypes, arising due to the effects of many genes acting in concert; and (ii) our epigenome - the cell-specific patterns of DNA methylation that determine, in part, whether or not genes are expressed, or not. Furthermore, there are ethical issues in providing information (e.g. on breast cancer "risk") to the general public, who may lack sufficient information to make informed decisions based on these complicated tests / results (Brewer et al., 2009; Tzeng et al., 2010).
The concerns / controversy regarding genetic testing (Bandelt et al., 2008; McGuire et al., 2010; Royal et al, 2010; see also the "Recent News, Headlines" bibliography, below) somewhat parallel those regarding DNA testing of ancestry. Companies that sell gene tests to help people trace their lineage offer no quality assurance guarantee, and need to strengthen the science behind their services. In 2009, five bioethicists published a paper in the journal Science - "The Illusive Gold Standard in Genetic Ancestry Testing" - calling for government regulation of genetic ancestry testing - also known as genetic genealogy (Lee et al., 2009).
That said, for persons of European ancestry, at least, it appears that "genes do mirror [ancestral] geography" (Novembre et al., 2008; Drineas et al., 2010).
Cited References
- Bandelt, H.J. et al. (2008) "The brave new era of human genetic testing." Bioessays 30:1246-1251. [PMID: 18937378]
- Brewer, N.T. et al. (2009) "When genomic and standard test results diverge: implications for breast cancer patients' preference for chemotherapy." Breast Cancer Research and Treatment 117:25-29. [PMID: 18785002] "Some women may be reluctant to forgo chemotherapy when genomic tests indicate low recurrence risk but standard criteria suggest high risk."
- Drineas, P. et al. (2010) "Inferring geographic coordinates of origin for Europeans using small panels of ancestry informative markers." PLoS One 5:e11892. [PMID: 20805874]
- Lee, S.S-J. (2009) "The Illusive Gold Standard in Genetic Ancestry Testing." Science 325:38-39 [DOI: 10.1126/science.1173038. PMID: 19574373]
- McGuire, A.L. et al. (2010) "Science and regulation. Regulating direct-to-consumer personal genome testing." Science 330:181-182. [PMID: 20929761]
- Novembre, J. et al. (2008) "Genes mirror geography within Europe." Nature 456:98-101. [PMID: 18758442
- Royal, C.D. et al. (2010) "Inferring genetic ancestry: opportunities, challenges, and implications." American Journal of Human Genetics 86:661-673.
- Tzeng, J.P. et al. (2010) "Women's experiences with genomic testing for breast cancer recurrence risk." Cancer 116:1992-2000. [PMID: 20213682] "This is among the first studies to describe patients' experiences with genomic testing for recurrence risk. Although many women understood discussions about their genomic test results, a third reported not fully understanding these discussions ...
Additional Sources of Information
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