A child inherits half its DNA from its mother and half from its father. It follows that information about the DNA of a set of persons may provide information about how they are related. Given DNA data and possibly additional information like age on a number of individuals, we may therefore address the question: “How are these people related”?
Our new book, Relationship Inference with Familias and R: Statistical Methods in Forensic Genetics, presents methods and freely available software to answer the question emphasizing statistical methods and implementation. The intended readership is researchers and practitioners of forensic genetics, as well as students in graduate courses. A large number of exercises with solutions are available.
Relationship estimation is crucial in many applications and not restricted to human applications. In fact, the last of four motivating examples of the first chapter is a “a paternity case for wine lovers” involving the relationship of Chardonnay, Pinot, and Gouais blanc.
Variations of classical paternity cases remain central worldwide. For instance, in Norway (5.1 million inhabitants) there are roughly 2000 paternity cases every year. Recent developments designed to deal with large, possibly inbred, families, mutations and missing data caused by degraded DNA are discussed. Identification of victims of disasters using DNA profiles of presumed relatives is handled using essentially the same framework.
Our work in this area has been closely linked to providing freely available software. The Familias program is the most widely used according to a survey conducted by the English Speaking Working Group of the International Society for Forensic Genetics. Further windows programs (FamLink and FamLinkX) have been developed to deal with linked genetic markers. In 2016, the software and methods have been presented in courses in Argentina, Denmark, Italia, Norway and Spain.
There is also an R Familias version which makes it easy for users to implement extensions that can be made available to the community. In addition, we present several other relevant R packages implemented by various authors.
The last three chapters (ch 5-8) of the book present the theory in a more general framework illustrated in the figure. This allows for extensions, and some standard, simplifying assumptions can be removed. For instance, the first four chapters assume allele frequencies to be known exactly. More generally, uncertainty in parameters can be accommodated. Forensic testing problems can be seen as more general decision problems, and the last chapter explains how.
The authors – Thore Egeland, Norwegian University of Life Sciences, Norway; Daniel Kling, Norwegian Institute of Public Health, Norway; and Petter Mostad, Chalmers University of Technology, Sweden – have created this video that describes their new book, Relationship Inference with Familias and R: Statistical Methods in Forensic Genetics, in more detail.
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