What does this number measure?
This represents about 2 m of cumulative nuclear DNA length for a diploid human cell before its DNA is replicated. This educational order of magnitude is published by OpenStax: the molecules of the 46 chromosomes are imagined unfolded and placed end to end. They do not naturally form one continuous molecule. This length is not doubled to count the two strands of each double helix separately. The catalogue's 12 µm neutrophil provides a concrete example of a nucleated cell; its diameter is not the diameter of its nucleus, and not all human cells have this size. DNA is compacted inside the nucleus. This scenario excludes mitochondrial DNA, haploid gametes and mature human red blood cells, which have no nucleus. A cell contains more DNA after replication. In the drawing, only the cumulative length is to scale: thickness and molecular details are enlarged to remain visible.
Compare the stated dimensions
The comparison uses the number in each fact sheet: altitude, height, diameter, length or distance, depending on the reference. Two values in metres do not necessarily describe the same property.
Source and limitations
A rounded value that depends on genomic content; there is no exact universal length for all cells. Ploidy, replication and individual characteristics change the amount of DNA. The molecules are conceptually placed end to end without adding connecting lengths; the illustrated thickness is not the actual diameter of the double helix.
An interpreted diagram of the cumulative length of unfolded nuclear DNA from a diploid cell. The 46 molecules are placed side by side conceptually; only the horizontal length is calibrated. Thickness, helices and breaks in the ribbon are symbolic, without claiming to represent 2 nm at this scale.