Tastes great, less filling

Nick Matzke posted Entry 1718 on November 28, 2005 06:21 PM.
Trackback URL: http://www.pandasthumb.org/cgi-bin/mt/mt-tb.fcgi/1713

A few months back, Nature published a series of papers on the completion of the chimpanzee genome, including a massive comparison of the human and chimp genomes (free online). One of the major utilities of having two closely-related genomes to compare (in addition to showing that humans and chimps have close common ancestors, as in Ken Miller’s testimony on Day 1 of the Kitzmiller v. Dover trial) is that genes that are evolving rapidly under natural selection can be detected.

At the time, an odd observation stuck in my head: not only were things like immune system genes evolving rapidly (as they do in apparently all mammals studied thus far – it’s a war zone out there with the microbes), but according to Table 4 of the Nature article, so were some olfactory and taste receptor genes. This seemed rather odd, given that humans are not exactly first among the beasts when it comes to sniffing capabilities, or, I presume, tasting (although according to this PNAS article, our “gustatory receptors” are doing rather better than our olfactory receptors, many of which have become pseudogenes).

Even with our modest capabilities in this area, however, there are evidently some pretty important things that at least our taste receptors can do. Protect humans from malaria, for example. Read Carl Zimmer’s latest to find out how.

Note: (I take a personal interest in this, because while in Zambia at the age of 7, I caught chloroquine-resistant malaria, even though I took my nasty, bitter chloroquine tablets every week. I was quite ill for a month (I was not diagnosed until I was back in the U.S. for some time, where malaria is not exactly the first diagnosis that comes to the mind of the typical doctor). So it was never quite “Evolution Schmevolution” for me.)

Another note: Today’s GROAN Award (GROAN = Gratuitous, Ridiculous, and Onerous Acronyms by Nerds) goes to HORDE, the Human Olfactory Receptor Data Exploratorium.

Yet one last note: If you’re wondering what that red thing is up at the front of the post, read about the episode of the cartoon The Tick entitled “The Tick vs. Science“, and focus on the mad scientist Dr. Mung Mung and his creation, Tongue Tongue.

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Comment #60609

Posted by Harald Korneliussen on November 29, 2005 3:18 AM (e)

What type of malaria was it? Was it one of the persistent ones? Ouch! My sympathies.

Comment #60622

Posted by drakvl on November 29, 2005 7:50 AM (e)

I knew I recognized that animation style!

Comment #60623

Posted by drakvl on November 29, 2005 7:54 AM (e)

I guess I should have thought of this before I submitted that last entry, but it didn’t occur to me until after.

My biology teacher told me about an Internet archive of the genetic sequences of various species. I’ve been trying to find it again, with little success. I know it’s an acronym with two Is in it, like HIMI or KIWI, but I can’t quite remember it. Can anyone help?

Comment #60635

Posted by Steven Thomas Smith on November 29, 2005 10:09 AM (e)

not only were things like immune system genes evolving rapidly … so were some olfactory and taste receptor genes.

Spoon!

Comment #60642

Posted by Bulman on November 29, 2005 11:27 AM (e)

Here’s an article from GenomeBiology.com that discusses the selection fo poor bitter receptors increasing the ingestion of cyanide. The low levels of cyanide in the body are in turn shown to be a selective adaptation that helps protect from malaria.

Comment #60645

Posted by Russell on November 29, 2005 11:46 AM (e)

From the article, linked above, about pseudogenes:

Olfactory receptor (OR) genes constitute the basis of the sense of smell and are encoded by the largest mammalian gene superfamily, with >1000 members.

Wow. That constitutes a sizable chunk of the total number of genes we’re supposed to have.

Two (related) thoughts:

(1) Here’s an experiment interesting to ponder, though probably ethically and practically beyond the pale. Suppose we could repair, by “gene therapy”, some OR pseudogenes. How would such an such an individual describe the experience of the odors undetectable by the rest of us?

(2) I wonder if the loss of function of those ORs was simply “allowed” because the detection of certain odors was not of much survival/reproductive value, or positively selected, because we’re actually better off without them?

[I guess Bulman’s comment about cyanide, added while I was editing this comment, is relevant to this.]

Comment #60650

Posted by Bob O'H on November 29, 2005 12:16 PM (e)

drakvl wrote:

My biology teacher told me about an Internet archive of the genetic sequences of various species. I’ve been trying to find it again, with little success. I know it’s an acronym with two Is in it, like HIMI or KIWI, but I can’t quite remember it. Can anyone help?

The main sequence database is called Genbank, which is severely lacking in i’s. The site is here. There’s also a bunch of links to sites
here. I hope some of them are interesting: have fun!

Bob

Comment #60757

Posted by Engineer-Poet, FCD, ΔΠΓ on November 30, 2005 2:32 AM (e)

I immediately recognized the image.  Great episode, great reference.

Comment #80511

Posted by semenax on February 17, 2006 5:14 AM (e)

Three phrases should be among the most common in our daily usage. They are: Thank you, I am grateful and I appreciate.

Comment #80675

Posted by semenax on February 18, 2006 7:08 AM (e)

Three phrases should be among the most common in our daily usage. They are: Thank you, I am grateful and I appreciate.

Comment #93070

Posted by penis enlargement on April 2, 2006 7:31 AM (e)

I agree with you the way you view the issue. I remember Jack London once said everything positive has a negative side; everything negative has positive side. It is also interesting to see different viewpoints & learn useful things in the discussion.

Comment #99005

Posted by enlargement on April 28, 2006 6:28 AM (e)

DISORDER is simply unrelated information viewed through some particular grid. But, like “relation”, no-relation is a concept. Male, like female, is an idea about sex. To say that male-ness is “absence of female-ness”, or vice versa, is a matter of definition and metaphysically arbitrary. The artificial concept of no-relation is the ERISTIC PRINCIPLE.