Question

A crime lab is using mitochondrial DNA as evidence in an upcoming case. Why is a crime lab MOST likely to use mitochondrial DNA instead of nuclear DNA as evidence in a case?

because human remains have been charred by fire
because the DNA sample is smaller than a quarter
because there are no human teeth or bones available
because the DNA sample is more than three years old

Answer 1

Mitochondrial DNA is more likely to be used when nuclear DNA is compromised due to factors like fire damage, small sample size, or age. It is passed down maternally and remains relatively unchanged, making mtDNA a reliable source for forensic analysis.

Step-by-step explanation:

A crime lab is most likely to use mitochondrial DNA (mtDNA) instead of nuclear DNA as evidence in a case for several reasons. Unlike nuclear DNA, which is subject to recombination and could be compromised due to the size of the sample, environmental conditions, or other factors, mtDNA is more durable and can be analyzed even from smaller or older samples. MtDNA is inherited maternally and passed down with few changes apart from rare mutations, providing a reliable genetic lineage. This property of mtDNA is particularly useful when remains have been charred by fire, as in such cases, nuclear DNA can be too damaged for reliable analysis. Thus, mitochondrial DNA offers a robust alternative for forensic identification when other forms of DNA evidence are not available or are in poor condition.