Human chromosomes. Coloured scanning electron micrograph (SEM) of a group of human chromosomes. These thread-like structures occur in the nucleus of every cell. They carry genetic information in the form of genes. Each chromosome consists of two strands (chromatids) joined in a region known as the centromere or kinetochore. Chromosomes are capable of making exact copies of themselves while the cell is resting between successive cell divisions. When chromosomes divide, the centromere splits longitudinally. Apart from the sex cells, every human cell contains 46 chromosomes, 23 of maternal and 23 of paternal origin. Magnification: x6,000 at 6x6cm size.