Which DNA type is commonly used when nuclear DNA is unrecoverable due to degradation, and why?

Which DNA type is commonly used when nuclear DNA is unrecoverable due to degradation, and why?

• A. Chloroplast DNA; because it is plant-specific.
• B. Ribosomal RNA genes; because they are conserved.
• C. Mitochondrial DNA; because it is present in many copies per cell.
• D. Mitochondrial DNA; because it is present in many copies per cell and more likely recoverable from degraded samples.

Answer: (D)

When DNA is degraded, recovering useful nuclear genetic information can be impossible because the nuclear genome is present in only two copies per cell and fragmentation often breaks those targets beyond usable length. Mitochondrial DNA is the go-to in these cases because each cell contains many mitochondria, each with its own genome, so there are thousands of copies of mtDNA per cell. That high copy number means that, even if some copies are damaged, enough intact mtDNA remains to be amplified and sequenced, making recovery far more likely from degraded material. Additionally, the mitochondrial genome is relatively small and analysis often uses short PCR targets, which further improves the chance of obtaining a usable result from degraded samples. Chloroplast DNA would not be appropriate for human samples since it is plant-specific. Ribosomal RNA genes are nuclear and, although present in multiple copies, do not offer the same high redundancy and recoverability from degraded human specimens as mitochondrial DNA. The combination of many copies per cell and suitability for short, amplifiable regions makes mitochondrial DNA the common choice in degraded cases.

When DNA is degraded, recovering useful nuclear genetic information can be impossible because the nuclear genome is present in only two copies per cell and fragmentation often breaks those targets beyond usable length. Mitochondrial DNA is the go-to in these cases because each cell contains many mitochondria, each with its own genome, so there are thousands of copies of mtDNA per cell. That high copy number means that, even if some copies are damaged, enough intact mtDNA remains to be amplified and sequenced, making recovery far more likely from degraded material. Additionally, the mitochondrial genome is relatively small and analysis often uses short PCR targets, which further improves the chance of obtaining a usable result from degraded samples.

Chloroplast DNA would not be appropriate for human samples since it is plant-specific. Ribosomal RNA genes are nuclear and, although present in multiple copies, do not offer the same high redundancy and recoverability from degraded human specimens as mitochondrial DNA. The combination of many copies per cell and suitability for short, amplifiable regions makes mitochondrial DNA the common choice in degraded cases.