What are Chromosomes?

Chromosomes are made of coiled DNA (deoxyribonucleinacid) and are found in the nucleus of every human cell. Although the number of chromosomes varies in each species, the amount of chromosomes in a species per body cell is identical. Humans have 23 pairs of chromosomes (diploid) or 46 individual chromosomes (haploid). However, comparison with other organisms shows that the number of chromosomes does not provide information about the developmental status of the species. While the blackbird has 80 haploid chromosomes, the mosquito has only 6 haploid chromosomes. The chromosomes are so condensed in the nuclei that they would come to a length of 2 meters when spread out.

The influence of chromosomes on our sex

In humans and a variety of animals, sex is determined by chromosomes. Here, we distinguish the gonosomes (sex chromosomes) from the autosomes. In humans, chromosome pairs 1-22 are autosomal and thus sex-independent, and the 23rd chromosome pair is responsible for sex determination.

In humans there are two different sex chromosomes, the X- and the Y- chromosome. Females have two X chromosomes at the twenty-third position, while males have one X and one Y chromosome, which can lead to hereditary diseases.

Sex-specific inherited diseases

If there is a gene defect on this single male X chromosome, it cannot be picked up by the other chromosome. Females have two X chromosomes at this location, so one healthy chromosome 23 can compensate for the defect in the other. The best-known examples of inherited diseases that therefore occur almost exclusively in males are red-green blindness, Duchenne’s muscular dystrophy, and hemophilia.