A. An unknown mtDNA sample is matched to a sample of nuclear DNA that was found at a crime scene
B. An unknown mtDNA sample is matched to a sample of mtDNA that was found at a crime scene
C. An unknown nuclear DNA sample is matched to a sample of nuclear DNA that was found at a crime scene
D. An unknown nuclear DNA sample is matched to a sample of mtDNA that was found at a crime scene
The correct option is B. An unknown mtDNA sample is matched to a sample of mtDNA that was found at a crime scene.
Mitochondrial DNA (mtDNA) is a type of DNA that is found in the mitochondria, which are the energy-producing organelles within a cell. Unlike nuclear DNA, which is inherited from both parents and can vary widely between individuals, mtDNA is inherited exclusively from the mother and has a relatively conserved sequence. Because of these characteristics, mtDNA typing can be used in forensic investigations to identify maternal relatives or to identify remains that may be too degraded for nuclear DNA analysis.
How is mtDNA used in forensic science?
In forensic science, mtDNA typing is used to match an unknown sample of mtDNA, such as from a hair or bone fragment found at a crime scene, to a known mtDNA sample, such as from a suspect or victim. If the mtDNA sequences match, it can provide evidence to support the hypothesis that the unknown sample and the known sample are from the same individual. This can be useful in cases where nuclear DNA is too degraded or unavailable, such as in ancient DNA samples or in cases where only a small amount of DNA is available.
In addition to identifying maternal relatives and degraded remains, mtDNA typing can also be used to exclude individuals from being related. For example, if a maternal relative is suspected of being involved in a crime, but their mtDNA sequence does not match the unknown sample, it can provide evidence to exclude them as a suspect.
Limitations of mtDNA typing
While mtDNA typing can be a valuable tool in forensic investigations, it has some limitations. One limitation is that mtDNA typing is not as specific as nuclear DNA profiling, as many individuals can have the same mtDNA sequence due to the fact that it is maternally inherited and does not undergo recombination. This means that mtDNA typing is less effective for individual identification than nuclear DNA profiling.
Another limitation is that mtDNA typing is not as effective as nuclear DNA profiling at distinguishing between closely related individuals. This is because mtDNA is inherited in a relatively predictable manner, so individuals who are closely related maternally are likely to have similar mtDNA sequences.
Finally, mtDNA typing is also subject to the same sources of error as other forensic techniques, such as contamination or human error. It is therefore important that proper controls and protocols are in place to ensure the accuracy and reliability of mtDNA typing results.