title: Mutation and mutation rates at Y chromosome specific Short Tandem Repeat Polymorphisms (STRs): a reappraisal.
abstract: Mutation is a topic of intense research and raises important problems in forensics. Since the markers of choice in current forensic genetics analyses are microsatellites or Short Tandem Repeat Polymorphisms (STRs), mutation is sufficiently common to cause difficulties in evaluating DNA evidence in a significant proportion of cases but at the same time rare enough to turn the estimation of the corresponding probability of occurrence into a hard task. We address these issues using the simplest model of transmission: the Y chromosome specific STRs. Within this model, and under an explicit set of definitions and involved assumptions, we developed the theoretical framework required for the study of allelic transitions in gametogenesis, identifying the required parameters and associated probabilities and finally we discuss the estimation of these parameters and their application in forensics. We conclude that (i) for forensic casework the relevant parameter for incorporation in a likelihood ratio is biallelic specific (i.e. the mutation rate estimate corresponds to the probability of the specific allelic transition observed) and (ii) for these estimates as well as in order to provide data for testing mutation models the absolute frequency of mutated and non-mutated transmissions per allele, along with the description of the observed mutations should be reported.
authors: IPATIMUP - Institute of Molecular Pathology and Immunology of the University of Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal.
authors: Nádia
authors: N
authors: Pinto
authors: IPATIMUP - Institute of Molecular Pathology and Immunology of the University of Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal; DNA Diagnostic Laboratory (LDD), State University of Rio de Janeiro (UERJ), Rio de Janeiro, Brazil.
authors: Leonor
authors: L
authors: Gusmão
authors: IPATIMUP - Institute of Molecular Pathology and Immunology of the University of Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal; Faculty of Sciences, University of Porto, Porto, Portugal. Electronic address: aamorim@ipatimup.pt.
authors: António
authors: A
authors: Amorim
mesh_terms: D041322:Chromosomes, Human, Y / Q000235:genetics*; D016172:DNA Fingerprinting; D030561:Databases, Nucleic Acid; D019075:Electrophoresis, Capillary; D005819:Genetic Markers; D005838:Genotype; D018095:Germ-Line Mutation; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D018895:Microsatellite Repeats; D010334:Paternity; D016133:Polymerase Chain Reaction; D020641:Polymorphism, Single Nucleotide
chemical_list: D005819:Genetic Markers
keywords: Forensics; Mutation; STRs; Y chromosome