Explain a challenge in interpreting two-person DNA mixtures and one strategy to address it?

Explain a challenge in interpreting two-person DNA mixtures and one strategy to address it?

• A. Mixtures are easy to interpret.
• B. Mixtures are straightforward and require minimal interpretation.
• C. Mixtures can obscure individual profiles; strategies include using Y-STRs to isolate male contributions.
• D. Mixtures can obscure individual profiles; strategies include using Y-STRs to isolate male contributions or applying conservative interpretation with peak height considerations.

Answer: (D)

Two-person DNA mixtures are hard to interpret because signals from both individuals merge in the profile, producing overlapping alleles and uneven peak heights that can obscure which alleles belong to whom. This makes it easy to miscall alleles or miss contributors, especially when one person is present in a much smaller amount or when alleles coincide at the same locus.

A common and effective way to address this is to use Y-STR analysis to isolate male contributions. Y-STRs amplify only the Y chromosome, so if a male contributor is present, their male-specific alleles can be identified even within a mixed sample. This helps separate the male component from any female or non-male DNA and clarifies the profile of the male contributor.

As an additional or alternative strategy, applying conservative interpretation that takes peak heights into account helps manage uncertainty. This involves using threshold criteria, considering stochastic effects and artifacts like stutter, and sometimes replicating analyses or using probabilistic approaches to avoid overcalling alleles from minor peaks. Together, these approaches make interpreting two-person mixtures more reliable.