There are 46 chromosomes in human somatic cells, which are called diploid cells (2n = 46). Gametic cells or sexual cells, are the haploid cells with a total of 23 chromosomes (n = 23). Of the 46 somatic cell chromosomes, 44 are called somatic or autosomes and 2 are sexual, gonosomes or heterosomes. Autosomes chromosomes are homologous pairs (one maternal and one paternal) and they are arranged in 22 pairs.
Each chromosome contains a DNA macromolecule. Chromosomes are transmitted during meiosis, transporting information and ensuring genetic continuity between generations. Chromosome contains one or two DNA molecules, depending on the cell cycle phase in which it is studied.
The increased chromosome variation in the size and shape required the formation of a classification system. The most used system is Denver, which divided human chromosomes into classes based on size, shape and the presence or absence of satellites. The human karyotype collect the 23 pairs of chromosomes in 7 groups: A, B, C, D, E, F, G.