scigirl

This thread is in response to the repeated claim of evolution-deniers that "evolution has not contributed anything to help humans."

I learned about an interesting example today in my cell biology class. As I hear or think of examples, I will continually update this thread.

Part 1) Endosymbiont theory explains the side effects of some antibiotics.

The endosymbiont theory states that around a billion years ago, prokaryotic ancestors of mitochondria were internalized by other anaerobic cells. This created a cell with a new organelle, which has a double membrane and its own genome.

This theory is based in part on the following observations when comparing bacteria and mitochondria:

• Both have circular DNA.
• Mitochondria have their own ribosomes (protein-making machinery), and the size of the rRNA component is more similar to a bacteria than to the cytosolic eukaryotic rRNA ribosome component.
• Proteins synthesized in the mitochondria have a formyl group added to them, like bacteria but unlike other eukaryotic proteins.
• There is sequence homology between the mitochondrial plasmid and bacterial DNA.

The second proof listed above, that mitochondrial ribosomes are similar to bacterial ones, has important medical implications. Some antibiotics (drugs designed to kill or inhibit bacterial growth) act by inhibiting bacterial ribosomes. Endosymbiont theory predicts that these drugs will also inhibit mitochondrial function.

From Molecular Cell Biology, 3rd edition, Lodish et al:
In this case, evolutionary knowledge will help medical researchers design better drugs to target bacteria in a different way, that does not simultaneously inhibit our very important mitochondria!

scigirl

Edited for silly spelling errors.

[ September 03, 2002: Message edited by: scigirl ]</p>

Dr.GH

This is very nice. And I am glad to hear a med student actually admit they learned something in their first two 'nonclinical' years. Then I taught in med schools, all the basic science profs were always irritated that students seemed to think everything they learned came from clinical rotations or the anatomy lab.

scigirl

Heh, well it could be because Denver SOM is very research oriented. In fact we are one of the few medical schools that teach a course in cell biology (the downside of this...if you fail, there is nowhere to retake it over the summer,you are held back a whole year )

The anatomy class is also heavily influenced by evolutionary biology and fetal development (to me these two fields are intricately linked of course). So I'm sure many of my "clinical correlates" of evolution I post here will come from anatomy class as well.

scigirl

LiveFreeOrDie

If I may briefly play devil's advocate here:

It seems to me that evolution and endosymbiosis are not the only reasonable explanations for the similarities between bacteria and mitochondria. Couldn't I also argue that the similarities point to a common designer for both systems? I could just as easily say that many antibiotic side effects are a result of bacteria and mitochondria being designed according to the same plan.

Oolon Colluphid

And the design reason for mitochondria having a very similar genome to Rickettsia prowazekii is...? The 'design' reason for them having their own totally separate genome at all (given that livers, kidneys, eyes, bones and brains are all encoded in nuclear DNA) is...?

Cheers, Oolon

LiveFreeOrDie

Reuse of an existing design?

gallo

Why? If you can poof an organism into existance in prefect working order, why is there any need to reuse design? Every "kind" could conceivably be its own design, right down to the genetic code.

pz

Whoa...this sounds like a very good place. I'll keep that in mind -- every year there's a big crop of students here who plan to go to med school, and I'll tell them where they should apply.

That is, in addition to telling all the really good students that they shouldn't waste their time with this medical school stuff, and should go to grad school.

MortalWombat

God's an object oriented programmer?

scigirl

Heh I've heard that plea before.

And I promptly ignored it!

Yeah denver is a good school, but it's hard to get into unless you are from colorado, or one of the WICHE states. They do accept a few "true" out of staters but it's rare.