Humans Have 46 Chromosomes, in 23 Pairs

Every species has its own number of chromosomes, the structures that carry DNA inside cells. The U.S. National Human Genome Research Institute states that humans have 23 pairs of chromosomes, for a total of 46. The number says nothing about how complex a creature is. The institute notes that a fruit fly has four pairs of chromosomes, a rice plant has 12 and a dog has 39. One human pair differs between the sexes. These are the sex chromosomes: females have two X chromosomes in their cells, while males have one X and one Y. Not every cell carries pairs. The only human cells that do not are the reproductive cells, which carry just one copy of each chromosome. The word itself comes from the Greek for color and body, because chromosomes are strongly stained by some dyes used in research.