|MadSci Network: Genetics|
Chromosomal loss in animals is usually lethal, and most of these individuals will not develop to the point of being born. There are a few exceptions to this of course depending on which chromosome is in fact missing. The loss of an autosome (non sex linked chromosome) is usually lethal as these chromosomes carry so many genes that the loss of 1 can led to the loss of biological functions, inability to produce certain proteins, lack of organ/body development and so on. There are cases in which it is possible to possess more then 1 copy of a chromosome, though this also can led to many problems, causing things like Down's Syndrome for example. Chromosome deletions can occur in relation to the sex chromosomes (the X and Y chromosomes), it is possible to only have 1 X chomosome. Instead of having the XX pair for females and the XY pair for males, you get a X0 which results in a disorder called Turner's Syndrome. Plants are more forgiving to the possession of multiple copies or missing chromosome then animals but the resulting individual will usually end up sterile and unable to reproduce itself. Moderator's note: Humans have 23 sets of chromosomes, but other organisms may normally have more or less. Some have only a couple, while others have hundreds. However, the gain or loss of chromosomes in all cases causes a change in the number or dosage of the genes, and is therefore bad news.
Try the links in the MadSci Library for more information on Genetics.