ABSTRACT
Admixture graphs are mathematical structures that describe the ancestry of populations in terms of divergence and merging (admixing) of ancestral populations as a graph. An admixture graph consists of a graph topology, branch lengths, and admixture proportions. The branch lengths and admixture proportions can be estimated using numerous numerical optimization methods, but inferring the topology involves a combinatorial search for which no polynomial algorithm is known. In this paper, we present a reversible jump MCMC algorithm for sampling high-probability admixture graphs and show that this approach works well both as a heuristic search for a single best-fitting graph and for summarizing shared features extracted from posterior samples of graphs. We apply the method to 11 Native American and Siberian populations and exploit the shared structure of high-probability graphs to characterize the relationship between Saqqaq, Inuit, Koryaks, and Athabascans. Our analyses show that the Saqqaq is not a good proxy for the previously identified gene flow from Arctic people into the Na-Dene speaking Athabascans.
Subject(s)
American Indian or Alaska Native , Genetics, Population , Humans , American Indian or Alaska Native/genetics , Bayes Theorem , Gene FlowABSTRACT
SUMMARY: Admixture graphs generalize phylogenetic trees by allowing genetic lineages to merge as well as split. In this paper we present the R package admixturegraph containing tools for building and visualizing admixture graphs, for fitting graph parameters to genetic data, for visualizing goodness of fit and for evaluating the relative goodness of fit between different graphs. AVAILABILITY AND IMPLEMENTATION: GitHub: https://github.com/mailund/admixture_graph and CRAN: https://cran.r-project.org/web/packages/admixturegraph . CONTACT: mailund@birc.au.dk .
Subject(s)
Genetics, Population/methods , Phylogeny , Sequence Analysis, DNA/methods , Software , Animals , HumansABSTRACT
Stoppage refers to changes in reproductive behavior following the birth of a child with a severe disease. The presence of stoppage can bias estimates of sibling recurrence risk if not properly addressed. If stoppage occurs non-randomly (differential stoppage), it is possibly an additional source of bias in sibling recurrence risk estimation. This study investigated whether stoppage occurs in Danish families with a firstborn child diagnosed with autism spectrum disorders, and if stoppage was differential. We found that stoppage occurs moderately in Danish families affected by autism spectrum disorders, and that stoppage is differential. However, differential stoppage is a minor source of estimation bias in Danish sibling recurrence risk studies of autism spectrum disorders.
