All organisms have a set number of chromosomes, and in humans that number is typically forty-six—twenty-three of these come from each parent, and twenty-two of these are paired, containing different versions of the same genes. The remaining chromosomes are the X and Y: women typically have two X chromosomes, men have an X and a Y. The genome is the total amount of DNA in an individual, or species, which includes all the genes, all the control switches, and more, much of which we don’t really yet understand.
