Secondary constrictions are useful in identifying a chromosome from a set.

The secondary constrictions are always constant in their positions and hence can be used as markers.

Secondary constriction is seen at the chromosome in addition to primary constriction/centromere.

At metaphase, a proteinaceous remnant of the nucleolus often remains associated with the secondary constriction.

An M1 cell probed with the No. 9 secondary constriction sequence Xb1 is shown in Figure 5.

At MII, the No. 9 chromosome can sometimes be identified by the stretched region on the long arm corresponding to the secondary constriction.

INF2-induced actin filaments may drive initial mitochondrial constriction, which allows Drp1-driven secondary constriction.

Besides centromere, secondary constriction can also be observed in some chromosomes, which if present in the distal region of the arm, would pinch off a small fragment called Satellite.

NORs include active rRNA genes, which give rise to secondary constrictions of metaphase chromosomes, and silent rRNA genes, which are often highly compacted in dense heterochromatin.