Tuesday, March 24, 2009
Malaria and CF
On page 179-181, Carroll speaks of how Malaria and the Typhoid fever bacterium greatly effected the abundance of both sickle cell disease and cystic fibrosis. The presence of these diseases, "shaped the evolutions of humans and may be responsible for the high incidence of particular genetic diseases" (180). In order to prevent these genetic mutations, drugs were administered to stop them at their source (by curing malaria or cf). My question is, is there any globally spread disease that has caused a beneficial mutation amongst the specimens it has infected? Are there any benefits to having an increased affinity to genetic mutations through disease?
Subscribe to:
Post Comments (Atom)
This comment has been removed by the author.
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteIn short, there are no diseases that have caused beneficial mutations amongst all of the species it has infected because the outcome of the mutation is largely context dependent. While some mutations are advantageous in certain contexts/environments, the same mutation in a different environment could have a very negative outcome. For example, bacteria that are exposed to antibiotics have mutations in the bacterial DNA that alter the target of the antibiotic, allowing the bacteria to survive. However, the mutation that allows the bacteria to survive may harm a protein or system that is important for the normal functioning of the bacteria i.e. enzymes in cellular respiration. An increased affinity to genetic mutations because of a disease could aid an organism in the right context; for example, people who have two mutant copies of the gene for a chemokine receptor known as CCR5 (also known as CKR5) are highly resistant to HIV infection. Also, people who do get infected with HIV but have one mutant copy of the CCR5 gene progress to AIDS more slowly than do people without the mutation.
ReplyDeletehttp://www.sciencemag.org/cgi/content/summary/273/5283/1797