Human chromosomes. Coloured Scanning Electron Micrograph (SEM) of several human chromosomes. These thread-like structures occur in the nucleus of every cell, and appear in this shape during cell division at metaphase. Chromosomes carry a person's genetic information in the form of genes. Each chromosome consists of two strands (chromat- ids) joined in a region known as the centromere or kinetochore. Chromosomes make exact copies of themselves while the cell is resting between cell divisions. When a chromosome divides, the centromere splits longitudinally. Apart from the sex cells, all human cells contain 46 chromosomes. Magnification: x2,250 at 6x7cm size.