Inferring the ancestry of parents and grandparents from genetic data

Inference of admixture proportions is a classical statistical problem in population genetics. Standard methods implicitly assume that both parents of an individual have the same admixture fraction. However, this is rarely the case in real data. In this paper we show that the distribution of admixture tract lengths in a genome contains information about the admixture proportions of the ancestors of an individual. We develop a Hidden Markov Model (HMM) framework for estimating the admixture proportions of the immediate ancestors of an individual, i.e. a type of decomposition of an individual's admixture proportions into further subsets of ancestral proportions in the ancestors. Based on a genealogical model for admixture tracts, we develop an efficient algorithm for computing the sampling probability of the genome from a single individual, as a function of the admixture proportions of the ancestors of this individual. This allows us to perform probabilistic inference of admixture proportions of ancestors only using the genome of an extant individual. We perform extensive simulations to quantify the error in the estimation of ancestral admixture proportions under various conditions. To illustrate the utility of the method, we apply it to real genetic data.

Neither as harmful as feared by critics nor as empowering as promised by providers: risk information offered direct to consumer by personal genomics companies

In this paper, I investigate ethical and policy aspects of the genetic services and web-rhetoric of companies offering genetic information direct to consumer, and I do so with a special focus on genetic risk information. On their websites, the companies stress that genetic risk testing for multifactorial complex medical conditions such as cardiovascular disease and cancer may empower the consumer and provide valuable input to personal identity. Critics maintain, on the other hand, that testing can be psychologically harmful, is of limited clinical and preventive value, and vulnerable to misinterpretation. I stress the importance of empirical studies in assessing the pros and cons of direct-to-consumer testing and point out that recent empirical studies indicate that this testing is neither as harmful as feared by critics nor as empowering as promised by the companies. However, the testing is not entirely harmless. Remaining problems include testing of third parties without consent and ownership of genotypic and phenotypic information. Moreover, the testing, although not particularly empowering, may still provide input to self-understanding that some people find valuable. Regarding policy-making, I suggest that self-regulation in terms of best practice guidelines may play an important role, but I also stress that national and international regulation may be necessary.