Finite-sample properties of family-based association tests.
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Alleles↗
Biomedical subjects
J C Whittaker
Publications and source records attributed to J C Whittaker.
Power comparisons of the transmission/disequilibrium test and sib-transmission/disequilibrium-test statistics.
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Alleles↗
Using information from both parents when testing for association between marker and disease loci.
Several extensions of the transmission/disequilibrium test (TDT) to multi-allelic markers now exist. In some of these, however, separate tests must be performed on male and female parents because of the non-independence of parental transmission patterns, reducing power, and complicating interpretation of the test results. Here we show that this non-independence is asymptotically irrelevant when using the allelic TDT of Bickeböller and Clerget-Darpoux [(1995) Genet Epidemiol 12:577-582], allowing the analysis of data from both parents simultaneously.
Alleles↗
The effect of family structure on linkage tests using allelic association.
We considered the problem of testing a marker for linkage with a disease, using tests based on the transmission-disequilibrium test (TDT). The power of such tests was investigated for a number of possible family types, for which the families were classified by the disease status of family individuals. We show that parental disease status greatly affects the power, with families containing a single affected parent often preferred over families in which neither parent is affected. Families with a pair of affected sibs are of great value for all situations considered, but extension of the TDT to allow inclusion of information from unaffected sibs rarely increases power, if the parents have been genotyped.
Adult↗
Randomization tests of disease-marker associations.
A powerful test for population association of a disease with alleles at a bi-allelic marker locus is the transmission/disequilibrium test (TDT). A generalization of the test to multi-allelic marker loci is proposed which utilizes the maximal association of individual alleles with the disease, given by the maximum TDT statistic, TDT(max). To overcome the multiple testing problem encountered when using the maximal association to test the null hypothesis of no disease-marker association, a randomization procedure is developed. An investigation of the power of the test suggests that the randomization procedure performs almost as well as a recently proposed likelihood based test of linkage disequilibrium. The advantage of the new test is that it can be applied sequentially, based on a one-sided version of the TDT statistic, for investigating patterns of association of several individual alleles with the disease.
Alleles↗
A likelihood ratio test for detecting patterns of disease-marker association.
A likelihood ratio test of disease-marker association is proposed, based on the observation of marker alleles transmitted from parents to affected children. The proposed association test has the advantage of identifying the population pattern of disease-marker association, differentiating between marker alleles that are positively and negatively associated with the disease. The power of the test for detecting association is evaluated and compared with three existing multi-allelic tests for some specific disease-marker association patterns. The power of the parametric tests depends crucially on the pattern of disease-marker association. An over-parameterised association model is less detrimental in terms of power than an under parameterised model.
Child↗
Using marker-maps in marker-assisted selection.
A method of using information on the location of markers to improve the efficiency of marker-assisted selection (MAS) in a population produced by a cross between two inbred lines is developed. The method is closer to mapping QTL than the selection index approaches to MAS described by previous authors. We use computer simulations to compare our method with phenotypic selection and two selection index approaches, simulations being performed on three genetic maps. The simulations show that whilst MAS can be considerably more efficient than phenotypic selection differences between the three MAS methods are slight. Which of the MAS methods is best depends on a number of factors: in particular the genetic map, the time scale under consideration ant the population size are of importance.
Chromosome Mapping↗
Multiple trial two strategy conflicts.
Much work has been done on iterated conflicts where the one-trial conflict is the Prisoner's Dilemma. The present paper is concerned with an iterated contest where the underlying contest has two pure strategies and the underlying payoff matrix is general; this therefore includes the Prisoner's Dilemma as a special case. By limiting the player's memory severely we can almost completely specify the Evolutionary Stable Strategies (ESS) of the two- and infinite-trial conflicts derived from this underlying payoff matrix.
Animals↗
A two-trial two-strategy conflict.
Iterated conflicts allow the possibility of co-operative-like behaviour in games such as the Prisoner's Dilemma. The present paper is an attempt to initiate the study of iterated conflicts when, (a) the number of iterations is fixed and finite and (b) the underlying payoff matrix is general, e.g. a mixed Evolutionary Stable Strategy (ESS) could occur in the non-iterated coflict. These assumptions are in contrast to the Iterated Prisoner's Dilemma. We consider a somewhat special case which none the less produces results of an interesting nature. For those cases where there is no internal ESS in the one trial case the two-trial case is easily resolved. When the former has an internal ESS then the two-trial case yields two ESSs whose supports are a partition of the space of strategies.
Animals↗