Nuclear DNA (nDNA)
Definition
The genomic DNA housed in the cell nucleus, packaged as 46 chromosomes in human somatic cells. The primary target for STR profiling and most forensic DNA typing. Diploid: approximately 6.4 billion base pairs per somatic cell.
- Location
- Cell nucleus
- Copy number
- 2 per somatic cell (diploid)
- Size
- ~3.2 billion base pairs per haploid set, ~6.4 billion diploid
- Primary forensic use
- STR profiling (autosomal, Y-STR, X-STR)
- Inheritance
- Biparental, one set from each parent
Common questions
Why is nuclear DNA preferred over mitochondrial DNA for individual identification?+
Nuclear DNA is biparentally inherited and highly polymorphic at STR loci, giving discrimination power in the range of one in billions between unrelated individuals. Mitochondrial DNA is maternally inherited and identical across all maternal relatives, so it can only exclude or narrow a maternal lineage, not individualise.
What happens to nDNA quality in degraded or old skeletal samples?+
Nuclear DNA degrades into progressively shorter fragments over time and with environmental exposure, which can cause dropout at longer STR loci. Analysts often switch to mini-STR kits with shorter amplicons, or fall back on mitochondrial DNA, which survives in higher copy number per cell.
How many cells are needed to recover a usable nDNA profile?+
A full STR profile typically needs the DNA content of a few dozen to a few hundred nucleated cells, though modern low-copy-number and enhanced PCR protocols can sometimes generate partial profiles from far fewer cells, at increased risk of stochastic effects like allele dropout.
Related terms
- Chromatin
- The complex of nuclear DNA wound around histone proteins in the nucleus. In forensic DNA extraction, chromatin must be disrupted to release...
- Cytoskeleton
- The protein scaffold within eukaryotic cells, composed of actin microfilaments, tubulin microtubules, and intermediate filaments such as keratin. Provides cell shape and...
- Eukaryote
- An organism whose cells contain a membrane-bound nucleus and other membrane-enclosed organelles. Humans, animals, plants, and fungi are eukaryotes. Most biological evidence...
- Mitochondrial DNA (mtDNA)
- DNA located in mitochondria rather than the cell nucleus. Present in hundreds to thousands of copies per cell, making it recoverable from...
- Prokaryote
- An organism whose cells lack a membrane-bound nucleus and organelles. Bacteria and archaea are prokaryotes. They are relevant to forensic biology in...