What is a significant limitation of mt-DNA analysis?

The significant limitation of mt-DNA analysis is that it cannot distinguish siblings or maternal relatives. Mitochondrial DNA (mt-DNA) is inherited only through the maternal line, which means that siblings from the same mother will share the same mt-DNA haplotype. Consequently, when mt-DNA is used in forensic analysis, it is able to show whether individuals share a maternal lineage, but it cannot specify whether two individuals are siblings or more distantly related individuals who share a common female ancestor. This limitation reduces the specificity of the analysis when trying to determine individual identity in cases where maternal relationships are involved.

The other options highlight different aspects of mt-DNA analysis. For instance, the notion that mt-DNA cannot be analyzed from hair can be misleading because hair, depending on the conditions of the sample and if it has sufficient amounts of cellular material, can be analyzed for mt-DNA. The option regarding large sample requirements may refer to nuclear DNA analysis, which typically requires a larger quantity of biological material than mt-DNA. Lastly, the applicability of mt-DNA decreasing in some scenarios doesn't reflect a fundamental limitation, but rather a contextual factor depending on the available evidence and case requirements.