Schlagwort-Archive: sibling

Once again genetic testing

I have argued earlier that the free decision of an individual to allow genetic testing, will also reveal data on genetic relatives that have never consented to that procedure.
A new review by Bruce Weir now confirms that “it is reasonably straightforward to find the probability of the genotypes of individuals when their relationship is known…” My current work lets me also assume that with 500,000 SNP data at hand, much individual characteristics of the donor can be reconstructed – there are no anonymous DNAs datasets as some people still believe.
I even fear that genetic testing will increase for example in “homeless” (in vitro fertilized) individuals as these people will want to prevent sibling marriage – see for example the a-China DNA project. Other people may be curious about their genealogy, others about drug side effect prediction, lifestyle, assurance questions…
With every new dataset, available datasets will gradually decrease their anonymity level. I fear that anonymity is not so much a dichotomous property, it is much more a likelihood ratio to stay unknown under the probability to be known. Yea, yea.

Addendum

Time online of Dec 17, 2006 reports that the British police is holding the DNA records of more than 1m innocent people — eight times more than ministers have previously admitted. I wonder if this will affect participation rate of the UK Biobank that targets health of lifestyle, environment and genes in 500,000 people.

What could have been learned from linkage studies

What makes the difference between genetic linkage and association studies? Simply speaking, for linkage you need to inherit a particular marker allele from your parents where it does not matter if a child in another family inherits another allele (pending it shares it with its affected sibling). With association studies this matters.

As we found with the much relaxed linkage strategy so many minor diverse loci, I assume a rather heterogeneous origin of complex diseases. There is no doubt about the importance of genes, but about the sharing of the same genetic abnormality. An (anonymous) position paper on basic Asthma Research Strategy II in Clin Exp All 2006; 36: 1326 says

The average size of effect on asthma and related traits from common SNPs is small. For instance, seven common SNPs in the IL13 gene jointly accounted for only 0,5% of the variance of total IgE … With a heritability of circa 60% for total IgE this implies that hundreds of genes, each with small effects, may be involved in IgE regulation.

Families presenting with a complex system disease will all have unique patterns how they arrive at the same clinical endpoint. Alpha-delta-gamma asthma, theta-kappa-jota schizophrenia or $%&# diabetes – are they combining lets say 3000 variations in 300 genes of 30 metabolic-signalling pathways to 1 disease of variable onset, severity and prognosis? Yea, yea.