Estimating Y-Str Mutation Rates and Tmrca Through Deep-Rooting Italian Pedigrees

Area of Science:

• Population genomics
• Human population genetics
• Forensic genetics

Background:

• Y-chromosome Short Tandem Repeats (Y-STRs) are vital for population genomics, forensics, and genetic genealogy.
• Accurate Y-STR mutation rates are essential for determining patrilineal relatedness and Time of Most Recent Common Ancestors (TMRCAs).

Purpose of the Study:

• To generate new Y-STR mutation rate estimates using a deep-rooting paternal genealogy approach.
• To assess the impact of mutations on TMRCAs in forensic and genetic genealogy contexts.
• To evaluate a Bayesian procedure for comparing observed and expected TMRCAs.

Main Methods:

• Typing 47 Y-STR markers in 135 individuals from 66 paternal genealogies in Northern Italy.
• Utilizing a genealogy-based approach to estimate mutation rates.
• Applying a Bayesian procedure (Walsh, 2001) to compare observed and expected TMRCAs, including the Infinite Alleles Model (IAM).

Main Results:

• The genealogy approach effectively yields reliable Y-STR mutation rate estimates, even with limited samples.
• Multi-step mutations and backmutations have a negligible impact on typical forensic and genetic genealogy timescales.
• A significant association was found between the number of mutations within genealogies and observed TMRCAs.
• The Bayesian procedure demonstrated good performance (up to 96.72%) for TMRCA comparison, particularly with the IAM.

Conclusions:

• The genealogy method is a robust strategy for estimating Y-STR mutation rates.
• Established Y-STR mutation rates are reliable for forensic and genetic genealogy applications.
• The Bayesian TMRCA calculation method shows high accuracy, especially when using the Infinite Alleles Model.