Chromosomes

The genetic information encoded in DNA and carried in cells is normally packaged in molecules called chromosomes: long strands of DNA and associated proteins that carry many genes, regulatory elements, and nucleotide sequences. Merriam-Webster Online Dictionary defines chromosome as “one of the linear or sometimes circular DNAcontaining bodies of viruses, prokaryotic organisms, and the cell nucleus of eukaryotic organisms that contain most or all of the genes of the individual.” It is derived from two Greek words: chroma, meaning color, and soma, meaning body.

Chromosomes were first observed by a Swiss botanist, Karl Wilhelm von Nägeli, in 1842 in plant cells. Belgian scientist Edouard Van Beneden independently observed chromosomes in Ascaris worms around the same time. Walther Flemming, a German anatomist, in 1882 discovered mitosis (the ...