29 March 2008

Weekly sampler 12

Shall we play a game? Recall Hugh Ross' fictional tale about the "team of physicists" that remade molecular genetics. Ross claimed, falsely, that:

They noticed that the quantity of "junk" in a species' genome was proportional to that species' degree of advancement.
The biological truth is the opposite: amount of DNA, "junk" or otherwise, is so uncorrelated with other aspects of biology that the situation was termed a paradox when it was first uncovered. Well...let's see the paradox in living color. In the next few Weekly samplers, I'll present you with some organisms (all animals) and we'll see how well you can guess their relative amounts of DNA (per genome) based on their "degree of advancement." Good luck! (Hint: use a quarter; it's easier to catch, and easier to find on the floor if you drop it.)

Which organism has the larger genome?

This one? Or this one?
1
2
3

Answers are here. Explanation can be found on the superb blog of one of the world's leading experts on genome size.

1. This story is 6 years old, but I never heard it till this week. A 52-year-old woman gets DNA testing to determine whether she can serve as an organ donor for her son. The tests reveal that she is apparently not the mother of two of her children. But...she is the mother of all of her children. How can this be?

She's a tetragametic chimera, meaning simply that her body is composed of cells descended from two genetically distinct embryos which evidently fused very early in development. Her ovaries are descended from one of those embryos, but her blood descends from the other. The result: she conceived children with gametes derived from one embryo, but her blood (which was used for the genetic tests) comes from the genetically-distinct other. Each of her cells has just one "parent", but as a whole she is derived from two distinct embryos, each of which arose from two distinct sperm/egg pairs; thus she, as a whole, is derived from four gametes instead of the typical two. Wild! And lots of fun for certain friends of mine who (like me) enjoy reflecting on human personhood and personal identity.

2. The newest issue of The Economist has an interesting piece on a large new European scientific collaboration.
“Explaining Religion”, as the project is known, is the largest-ever scientific study of the subject. It began last September, will run for three years, and involves scholars from 14 universities and a range of disciplines from psychology to economics. And it is merely the latest manifestation of a growing tendency for science to poke its nose into the God business.
Bring it on!

3. This View of Life is a nice-looking site that aims to be "a beginner's guide to a science-based understanding of evolution." I'd love to hear some feedback from anyone who's checked it out. (Via the ASA listserv.)

4. Read Ryan Gregory on the much-abused concept of Just-So Stories.

5. Earlier this week, I heard an interesting story on MarketPlace about "video games that are good for you." I think I'll ditch Text Twist and try this instead. The games "reduce stress and boost self-confidence." Do they have any that add time to the day?

6. At the Howard Hughes Medical Institute (HHMI), a site called BioInteractive is crawling with "free resources for science teachers & students." Lectures, animations, "virtual labs." It's a mixed bag, but very much worth a stroll. (Via Panda's Thumb.)

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