Department of Chemistry, Biotechnology and Food Science, The Norwegian University of Life Sciences, PO Box 5003, NO-1432 Aas, Norway

Centre for Mathematical Sciences, University of Cambridge, Cambridge, UK

Dipartimento di Economia, Università Roma Tre, Rome, Italy

Department of Mathematical Sciences, Chalmers University of Technology and University of Gothenburg, Sweden

Department of Forensic Genetics and Forensic Toxicology, The National Board of Forensic Medicine, Sweden

Abstract

Mutation models are important in many areas of genetics including forensics. This letter criticizes the model of the paper 'DNA identification by pedigree likelihood ratio accommodating population substructure and mutations' by Ge

Please see related letter:

Correspondence

In a paper in

where

Apparently equation (8) does not define a probability distribution since summing over

Below we interpret 'Equal probabilities for gaining or losing repeats are assumed' to mean that a scaling factor 1/2 should be inserted on the right hand side of equation (8) since this leads to a proper probability distribution summing to 1.

There are several problems with this model. Most importantly, it allows for alleles with zero or negative repeat numbers which is not meaningful. Furthermore, this may also be a practical problem. For instance, using the mutation model for marker THO1 having allele value of three repeats leads to an allele with a value less than or equal to zero with probability 1.25 × 10^{-6}. While this probability, based on parameter values α = 0.95 and μ = 0.001 suggested in

Ge

Ge

Competing interests

The authors declare that they have no competing interests.

Authors' contributions

TE wrote most of the manuscript. All the authors contributed, read and approved the manuscript.