Too Few, Too Many

Abstract

To organize the vast amount of DNA, it is divided and packaged into discrete units in cells called chromosomes. This convenient organizational structure enables the DNA material to be easily split each time a cell grows and divides, so that every cell ends up with the exact same amount of DNA. Humans have 46 pairs of chromosomes, half inherited from their mother and half from their father. If a cell ends up with fewer or greater number of chromosomes by mistake, this can result in a disease or the cell will otherwise shut down and die (due to a sort of information overload). Many genetic syndromes such as Down syndrome are due to an extra chromosome. In addition, many cancers have extra or missing chromosomes or sometimes an extra or missing part of a chromosome. New genomic technologies enable accurate detection of the chromosomal number and structural changes that may be linked to disease.