The Backstreet Boys released a new album. I never thought I’d start a science article—or any article—with that sentence, but here we are.
We are here because the promotional artwork for the album (above) is a photograph of the boy band (man band?) lit by a projection of DNA bands. The image, and the album’s title, DNA, jumped out of my Twitter timeline because I’m a geneticist, I work with DNA, and I’ve seen countless images just like it in textbooks and research articles. I’ve even made them myself in the lab.
What struck me as funny (both funny-ha-ha and funny-odd) is that the lab methods that could have produced this image are old—older even than the Backstreet Boys’ first album. One of the methods—called Sanger sequencing—was published in 1977, making it even older than two of the Backstreet Boys themselves, scientist Kristy Lamb pointed out. Genetics is a particularly fast-moving science. New technologies are constantly emerging and eclipsing prior ones. Yet this 40-year-old imagery persists, and not just in the promotional artwork for DNA. Just do a Google image search for “DNA sequencing” and you’ll see plenty of images like this mixed in with the double helices and long GATTACA readouts.
Named for Frederick Sanger, who shared the 1980 Nobel Prize in Chemistry with Walter Gilbert for its invention, Sanger sequencing involves reproducing DNA’s natural copying mechanism in a test tube, making millions of copies of a stretch of DNA of interest. (Technically, Sanger and Gilbert shared half of the Nobel; the other half went to Paul Berg for other research on the biochemistry of DNA.) In the tube, along with the starting DNA, are the ingredients needed for DNA replication, including nucleotides—the A’s, T’s, G’s, and C’s that are the building blocks of DNA. The mix is divided into four tubes, each of which is spiked with a very small amount of a special, modified version of just one of the four nucleotides. When one of these special nucleotides is incorporated, it causes the early termination of the growing strand.
The result is four tubes of DNA fragments of many different sizes. In the “A” tube, the lengths of the fragments correspond only to the lengths of the DNA strand that terminate with an A. Similarly, in the “T,” “G,” and “C” tubes, the fragment lengths correspond only to the lengths of the DNA strand that end with those nucleotides.
Finally, you are ready to separate and visualize the DNA fragments in each tube by size, from long to short. The contents of the tube are separated in an electrified gel matrix in a long vertical “lane,” with the four lanes right next to each other. The resulting pattern of bands lets you “read” the DNA from beginning to end.
It looks like this:
Careful readers might have noticed that I suggested there was more than one method that produces images like this. At first glance, I thought the projection in the Backstreet Boys’ publicity photo was modified from an image made with Sanger sequencing. But when I looked again in preparation for writing this article, I had second thoughts. Why aren’t the lanes clustered in groups of four? Why are some of the bands in adjacent lanes the same size? (They shouldn’t be if you’re doing Sanger sequencing.) It could be that the photo was heavily modified with individual lanes copied and pasted. Indeed, some of the lanes are even identical to each other (*suppresses fake ivory tower scoff*).
Or it could be that this image was made with another old method: DNA fingerprinting. Made famous in so many crime TV shows, DNA fingerprinting was invented in 1984 by Alec Jeffreys, who, though he did not win a Nobel Prize, was made a knight of the British Empire for his contribution to science, among many other prestigious awards, which is nice.
While both methods involve separating DNA fragments based on size, DNA fingerprinting does so at a lower resolution than Sanger sequencing. Instead of reproducing DNA replication in a test tube and making different fragment lengths with special nucleotides, a DNA sample is chopped into pieces with special molecular scissors called restriction enzymes. They cut DNA only in certain specific places in the DNA. Because everyone (except identical siblings) has slight differences in their DNA sequence, the fragment lengths generated by using restriction enzymes vary from person to person. When you separate the fragments, one person’s pattern looks slightly different from another’s, allowing you to trace family relationships and even establish the identity of an individual person (or an individual of any other species).
This is a DNA fingerprinting image:
I suspect the Backstreet Boys weren’t going for a tongue-in-cheek reference to their own advancing age. While today’s DNA sequencing methods produce images that scarcely resemble those produced by Sanger sequencing and DNA fingerprinting, the old-school imagery is still everywhere. The Backstreet Boys’ promotional team probably just went with a stock image that looked compelling and worked well as a projection.
But that doesn’t answer the real question: Why is 40-year-old imagery still so ubiquitous? As science writer and editor Stephanie Keep tweeted, one reason may be that, despite its age, the Sanger method is still taught in high school classrooms: “It’s so visual and intuitive.” It’s true. When I teach students about DNA sequencing, I always start with Sanger sequencing and use that as the basis for explaining newer technologies, adding more complexity as I go, following the historical timeline.
Another reason the old imagery is still in use may be that the images produced by newer, so-called next-generation sequencing methods aren’t visually scored by a scientist sitting at a lab bench, but by computers. As such, the images themselves often go unseen by human eyes, despite their colorful beauty.
But why did the Backstreet Boys call their album DNA in the first place? The official RCA Records press release announcing the album says, “BSB analyzed their individual DNA profiles to see what crucial element each member represents in the groups DNA.” It links to a YouTube video that supposedly explains “how their individual strains, when brought together, create the unstoppable and legendary Backstreet Boys.”
The video is a futuristic, spy movie–esque montage, complete with a computerized female voice describing the various characteristics of each Backstreet Boy. Reader, I confess: I cringed. There were so many tropes and misconceptions about DNA packed into the 83-second video, I would have to write a follow-up to this just to explore them. The cringeworthiness doesn’t end there, though. The cover of DNA has each Backstreet Boy on his own spiral staircase.
The staircases are surely meant to evoke the structure of DNA: the famous double helix. But there’s a problem, as the social media account for the journal Genome Biology tweeted: The staircases are spiraling in the wrong direction. DNA is usually right-handed. If you stick out your right thumb, your fingers will naturally curl in a right-handed spiral as you move your hand in the direction your thumb is pointing. The Backstreet Boys’ staircases are left-handed.
But hey, they want it that way, so who am I to argue?