Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
I’ve been feeling like this all week:
A while back I posted many pictures of shaved cats, but none as scary as this. Now some of you are going to ask why anyone would do this to a kitteh. There are several reasons, the most plausible being to keep a longhaired animal cool in the summer. One of these “lion cats” lived behind me when I was in Maryland. Alternatively, the cat’s fur could have been irreparably tangled.
I hadn’t heard of this show before, but then I’m rarely in Britain, and when I am I don’t have much time to listen to the radio. That said, I have enjoyed BBC Radio 4, which I believe is the British equivalent of National Public Radio. Today I’ll be on the Moral Maze broadcast at 2 pm Chicago time (8 pm GMT). You can listen on the internet for free at this site. Past shows seem to be archived as podcasts here.
I’m told that the broadcast, which lasts 45 minutes, will involve a panel of four debaters who chew over a single moral issue among themselves, and then question a number of “witnesses” who have already been interviewed and have known positions on the issue. Today’s topic will be the relationship between science and morality, and I am one of the witnesses. (The panel includes Kenan Malik and Claire Fox). Yesterday morning I was interviewed for a long time by a researcher, who fired questions at me about morality, concentrating heavily on Sam Harris’s new book, The Moral Landscape. This was a way of vetting me for radio-worthiness—I think the panel also fires questions at the witnesses.
Judging by the rigor of the researcher’s questions, these people know what they’re about, so it should be an interesting show.
Insofar as I have any “philosophy” about how I do my work, it’s this: keep experiments simple. I’ve always tried to do experiments sufficiently uncomplicated and easy to understand that the results—one way or the other—would be clear-cut enough to not require (or barely require) statistical analysis. I’ve taught my students this notion, too, and I think I’ve succeeded in that endeavor.
And the experiments I most admire are equally simple. The most beautiful, as I’ve mentioned before, is Meselson and Stahl’s demonstration, in 1958, that the replication of DNA was “semiconservative”: that is, when a two-stranded DNA molecule replicates, it unzips and each strand forms a template for building a new strand from nucelotide and sugar constituents. (There are many other ways DNA could have replicated.)
The results of this experiment were crystal clear: they involved first marking all the DNA strands in bacteria with a heavy isotope of nitrogen (you can do this simply by giving the bacteria Purina’s heavy-nitrogen E. Coli Chow). They then put those bacteria into medium that had “light” nitrogen, extracting the bacterial DNA at various intervals—as their DNA replicated—and centrifuging it in a cesium chloride density gradient. This enables you to see which strands have the heavy nitrogen and which don’t, for the different-weight strands move to different positions in the chemical gradient; and various theories of how DNA replicates predict different patterns for how the strands will migrate. I’d recommend simply downloading the Meselson and Stahl paper at the link below to see how clean the results were. You don’t have to be a scientist to understand how the experiment worked, and what it means. (This, and the experiment following, are all described beautifully in Horace Freeland Judson’s The Eighth Day of Creation.)
Below is figure 4 from Meselson and Stahl’s paper, which shows absolutely, and without any need for mathematical analysis, that DNA replicates semiconservatively. See how a “heavy” (high-weight) band starts giving rise to a lighter band within one generation (a DNA molecular that’s half the original “light” one and half the new “heavy”one). Lighter-weight bands are to the left. And then, after another generation of DNA replication (the bacterium E. coli replicates every 20 minutes), you see even lighter bands, now consisting of the newly formed light strands which have themselves become templates for yet another light strand—giving rise to “double light” DNA. Read from the top down: from the beginning of the experiment to the end, note how heavier bands produce semi-heavy bands (half old, half new DNA) and then fully light bands (all new DNA).
Lighter-weight bands are to the left:
This is what scientists call “a clean result”
The second most beautiful experiment, which took place fifty years and one week ago, was done by Marshall Nirenberg and J. Heinrich Matthaei, and is the subject of a really nice article by our pinch-“blogger” Matthew Cobb in yesterday’s Telegraph “Genes and DNA: meet the first man to read the book of life.” The piece is really about Matthaei, who did the crucial experiment, in 1961, that began the decoding of DNA. By “decoding”, I mean understanding how the sequence of four nucleotide “letters” in DNA (adenine, guanine, cytosine, and thymine [which is “uracil” in the RNA product produced by DNA]) codes for amino acids, the constituents of proteins. After all, what DNA “does”, by and large, is code for proteins.
It had been theorized by George Gamow that because there are 4 DNA bases and 20 amino acids, the code was probably a triplet code, since with 4 bases a doublet code could only yield 16 (4 X 4) amino acids. Unravelling this code was one of the major accomplishments of modern biology, and was begun by Nirenberg and Matthaei in Nirenberg’s lab at the National Institutes of Health. As Matthew describes, the crucial experiment was actually done by Matthaei while Nirem=nberg was away. Setting it up was complicated, for it required constructing a system of “cell-free” protein synthesis, made by using the cell contents of bacteria. Once in place, the researchers could use artificially constructed RNAs (the product of DNA that itself codes for proteins) to see what proteins could be produced by RNA in the artificial system.
As described on pp. 473-480 in The Eighth Day of Creation (buy that book!), the crucial experiment, called “27Q,” was begun at 3 a.m. (!) on May 27, 1961. It was over six hours later. Matthaei determined that an artificial strand of RNA composed only of the nucleotide base uracil (“poly-U”) produced proteins containing only phenylalanine. Thus “UUU” (or “UUUU” or higher polymers; they didn’t yet know the code was triplet) coded for that amino acid. They cracked codes for other amino acids as well. As Matthew describes in his piece:
The discovery was finally revealed two weeks later in Moscow, at the Fifth International Congress of Biochemistry. Nirenberg was given 15 minutes to present his findings – but only a handful of people turned up to hear a nobody claim he had solved a problem that was still defeating the world’s largest laboratories. When the news reached Francis Crick that afternoon, he immediately changed the conference programme so that the young American could give his talk again. The next day, in front of a packed lecture theatre, Nirenberg described his careful experiments and created a sensation. When he stepped on to the stage, Nirenberg also stepped into history.
By the end of the year, Crick had shown that the DNA code was a triplet code, and that code had been cracked for every amino acid.
Nirenberg stepped into history, but Matthaei only got his toe in. For in 1968 the Nobel Prize for Medicine and Physiology was given to Robert Holley, H. Gobind Khorana, and Marshall W. Nirenberg for uncovering the relationship between DNA sequences and proteins. Matthaei was left out in the cold. (Nobel Prizes in one area cannot be given to more than three people in a given year). This is quite unjust, since Matthaei had done the crucial experiment and was also pivotal in setting up the cell-free synthesis system. As usual, the boss gets the prizes and the grunts get squat. I consider Meselson and Stahl’s lack of Nobels equally unjust.
Nirenberg died last year, but what happened to Matthaei? Surprisingly, even at age 82 he still goes to the lab, bicycling to the Max-Planck Institute every day. You can see a video of him and an interview (in German) here. What a trouper!
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Meselson, M. and F. W. Stahl, 1958. The replication of DNA in Escherichia coli. Proc. Natl Acad Sci USA 44: 671–82. doi:10.1073/pnas.44.7.671
Nirenberg, M. W., and J. H. Matthaei. 1961. The dependence of cell-free protein synthesis in E. coli upon naturally occurring or synthetic polyribonucleotides. Proc Natl Acad Sci U S A 47:1588-602.
Did you know that falcon chicks are called “eyases“? That’s a new one on me. At any rate, the four peregrine eyases at Falconcam (now named Wilbur, Dewey, Lincoln, and Rosalind) were banded this morning, their nest lined with fresh gravel, and the camera window cleaned. Go here to watch a short video of them being returned to the nest (in a cardboard box!), and hear how much noise four ticked-off eyases can make.
Here’s a screenshot. Those babies are LOUD!
Reader Phil Garnock-Jones, an emeritus professor of biology at Victoria University of Wellington, New Zealand, sent us a noble and leonine cat:
This is our 8 year old Abyssinian, Rufus; he was a birthday present for my partner Sabrina. He’s a ballsy cat, but only figuratively speaking, known up and down our street for going into other people’s houses stealing their cats’ food, and beating up any dog that comes up the street. So although he’s a pedigree cat, he’d probably do very well as a stray. His collar tag has his name and our phone number, so he’s locally notorious; neighbors say “Oh, so YOU’RE Rufus’s people”, with just enough of a judgmental tone that we know they don’t fully approve. He’s a good mouser and very athletic. Occasionally he gets grumpy and whacks one of us, but mostly he’s very affectionate. He’ll jump from the floor into anyone’s arms—you have to catch him—and will smooch, with his arms around your neck. More often he picks on our other cat Lila, who is a lilac Abyssinian, half his weight, and very sweet, but they cuddle up together at night.
Abyssinians are a bit mad and hyperactive. Ours still behave like kittens at times. When they were young they wandered a lot, in at least a 1 km radius of home, but now they stay closer unless we deliberately take them for a walk. Then, they’ll trot along with us quite happily for a kilometre or two.
Although the kitteh contest has long been closed, readers are still sending me photos and short but interesting descriptions of their cats. If you have one, by all means send it along. I can’t always promise to use it, but I haven’t rejected one yet . . .
George Church is a well known molecular geneticist who helped design the first “direct” method of DNA sequencing, and played an important role in initiating the Human Genome Project. He has an appointment at Harvard University and consults for several companies. His latest endeavor is the Personal Genome Project, designed to get DNA sequences from many individuals with the aim of curing genetic maladies.
Church also has a Reddit page in which he answers readers’ questions. Sadly, there he shows a chronic and debilitating sympathy for religion:
Is there evidence of God in science?
Some people feel that science and faith have nothing in common. But a considerable amount of faith drives everyday science — and frequently religion addresses scientific topics (e.g. the physics/biology of miracles, ancient gods, Galileo). If faith had no impact on our physical brain, then by what mechanisms does it impact our spoken conversations. Billions of humans (in a very real scientific sense) have faith. The overlap is vast and fertile. As we learn more about nature, for many of us, this greatly strengthens rather than lessens our awe.
Sad, isn’t it, that a really smart scientist makes an assertion that “a considerable amount of faith drives everyday science.”
Let us once and for all make the distinction between the scientific and religious notions of faith—before they’ve become deliberately and permanently conflated by the faithful:
FaithSCIENCE : Confidence, based on mountains of experience, that answers to questions about reality are best derived from a combination of evidence and reason.
FaithRELIGION : Confidence, based on no experience (indeed, even contrary to experience), that answers to questions about “reality” are best derived from personal revelation, authority, scripture, and dogma.
You may remember that last December the Dallas-Forth Worth (Texas) Coalition of Reason put up messages on four Fort Worth buses proclaiming, truthfully, “Millions of American can be good without God.” And you may also remember that a group of peeved Christians hired another truck, emblazoned with a counter-message (“I still love you—God”), to follow the bus around for a month. Here is the pair:
Reader Sigmund, who posts hilarious parodies of faith and accommodationism at his Sneer Review website, had a Bright idea for the accommodationists: make your own chase truck! And he even designed one:
If you’re not a visitor to Sigmund’s website, stop by from time to time (he posts sporadically). Among his brilliant creations are Rock Stars of Accommodationism, The Not Very Nicean Creed, Bohemian Rosenau, and, of course, his masterpiece video, The Downfall Chris Mooney’s Unscientific America.
The four peregrine falcon chicks nesting at the Evanston Public Library (just north of Chicago) will be banded today (Tuesday) at 11 a.m. Chicago time (5 p.m GMT). It will be broadcast live on our FalconCam.
Here’s a picture of Banding Day from a few years ago; note that it happens right inside the library.
