Many of you will recall that chromosomes carry the genetic material, and almost every cell in our body contains two copies of each chromosome. Humans have 23 different chromosomes that make up a set, and so the two sets add up to a total of 46 chromosomes. Because we have two sets, we are said to be diploid, meaning of all things, two sets! So what's all of this adding up to, and what does it have to do with deserts? Well, it seems that in plants, sometimes you accidentally end up with more than two sets of chromosomes. Three sets forms a triploid, four sets a tetraploid, six sets a hexaploid, and eight sets—well, you get the idea.
The reason for this genetics lesson is that our Chihuahuan Desert
creosotebush is diploid, with two sets totaling 26 chromosomes; but in the Sonoran
Desert, the plant is tetraploid, with four sets; and in the Mojave Desert, hexaploid,
with six sets adding up to 78 chromosomes. As between humans, sometimes what's
within differs far more than appearance would indicate.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.