Chromosome

What is a chromosome?

At the beginning of the 20th century the chromosomes have been identified as the carrier of the hereditary disposition. Chromosomes are located in the nucleus of each cell and consist of long DNA strands. Only when the DNA is tightly coiled many times around specific proteins (called histones) during cell division, the shape of the chromosomes become visible under a microscope. The constriction point of a chromosome - the centromere - is conspicuous. After duplication of the DNA for an upcoming cell division, both DNA strands are held together in the centromere. The location of the centromere gives the chromosome its characteristic shape. The end pieces of the chromosomes are called telomeres.

Each somatic cell of the human body has 46 chromosomes consisting of 23 pairs of chromosomes. Each pair is composed of one chromosome from the mother and one chromosome from the father. One pair - the sex chromosomes - is responsible for determining the gender. This is the XY pair in men and the XX pair in women. The remaining 22 pairs of chromosomes are called autosomes.