Even just having extra quantities of the same DNA can cause enormous differences. Edward’s syndrome (extra copy of chromosome 18) means most do not survive long enough to be born and few live past 1 year of age. Patau syndrome is much the same story with chromosome 13 although in that case sometimes only portions of the chromosome are duplicated and the child lives a bit longer. And of course there is Down’s syndrome (extra chromosome 21) which is better known. This duplication can happen with any chromosome. These are just those which happen more often and survive longer. Many are miscarried so quickly that they are not aware of being pregnant.
Of course… I am not a biologist (like glipsnort… so I certainly wasn’t trying to inform him of these things). I just love looking these things up. Just today I was telling family members about another thing I investigated. So many cuisines around the world use red pepper I wondered what people did before the discovery of America which is where all such peppers come from. Well not quite all pepper. There is black pepper (which came from India) and it turns out there were variants of black pepper used around the world before these American peppers were discovered, such as long pepper, as well as an unrelated Sichuan pepper used in China with quite a different culinary effect. Otherwise we just had such things as mustard, ginger and cinnamon to add spice to the experience of life.