The new Star Trek series gets biology terribly, terribly wrong.

The new Star Trek: Discovery series is based on a massive scientific error. Can it survive?

It didn't have to be this way. Those of us who have followed Star Trek through its many TV series and movies, including the excellent trio of recent moves (2016's Star Trek Beyond is the latest) were eager to jump on board the newest show, Star Trek: Discovery.

Despite some rather uneven acting in the pilot, I was willing to give it a chance. So were millions of other Star Trek fans.

But alas, the writers have stumbled into a scientific error so egregious, and so entangled in the entire plot line, that I fear the new Star Trek cannot recover. (Note: a few mild spoilers ahead.)

Episodes 4 and 5, released on October 8 and 15, revealed that the USS Discovery, the ship that the series revolves around, has an advanced form of transport that allows it to travel anywhere in the universe instantaneously. Unlike all previous Star Trek transport tech, this one uses a biological mechanism, based on mushrooms.

Yes, you read that right. The DASH (Displacement Activated Spore Hub) drive uses mushroom spores as its power source. They've discovered a special fungus whose root system extends "throughout subspace" all over the galaxy. Using spores from this fungus, the ship can jump into subspace (or something like that) and jump out somewhere else in real space, light years away, in a matter of seconds. As bizarre and this sounds, the worst is yet to come.

To power its DASH drive, the Discovery maintains a large greenhouse full of spore-producing mushrooms. (Mycologists might love this, but how big a fan base can they be?) The problem for the Discovery, in the first few episodes, is that the experimental drive will only let them jump short distances.

Then they discover the tardigrade. Tardigrades are a real thing: they are microscopic animals, only 0.5 millimeters long, that live all over the planet. Here's a picture of one:

Electron microscope image of Milnesium tardigradum,
from E. Schokraie et al., PLoS ONE 7(9): e45682.

They are also surprisingly cute for a microscopic animal, and they are colloquially known as water bears, moss piglets, or space bears. "Space bears" comes from their ability to survive in extreme environments, possibly including interplanetary space.

Star Trek Discovery's tardigrade is, shall we say, rather different. It looks a bit like the picture shown here, but it's the size of a large grizzly bear, incredibly strong, and extremely fierce. On the show they call it a "giant space tardigrade."

But that's not all. Thanks to a unique biological property that the show's writers apparently misunderstood, the space tardigrade can access the mushroom network to travel throughout the universe, wherever and whenever it chooses.

Here's how the space tardigrade accomplishes this remarkable feat of interstellar travel, as explained by Michael Burnham, the show's central character (in Episode 5, "Choose your pain"):

"Like its microscopic cousins on Earth, the tardigrade is able to incorporate foreign DNA into its own genome via horizontal gene transfer. When Ripper [the space tardigrade] borrows DNA from the mycelium [the mushroom], he's granted an all-access travel pass."

And just like that, not only the tardigrade but the entire spaceship jump across the galaxy. Is this sounding a bit crazy? It should.

Horizontal gene transfer (HGT) is a real thing. It's a process through which bacteria sometimes take up DNA from the environment and integrate it into their own genomes. Animals can't do HGT, but rather infamously, a paper was published in December 2015 that made the bold claim that tardigrades had a unique ability to absorb all kinds of DNA. That paper was instantly controversial in the scientific community, and not surprisingly its findings were being disputed in the Twittersphere within days of its appearance. Surprisingly, the same journal (PNAS) that published the bogus HGT claim published a second paper just a few months later showing that tardigrades do not absorb foreign DNA into their genome. That plus a third paper showed that the original paper had mistakenly identified contaminating DNA as part of the tardigrade's own genome. This rapid correction of the record was a win for science; I've used this example to demonstrate to my undergraduate class how sloppy science (the first paper) can lead one astray.

So: a minor scientific controversy, quickly debunked.

Until, that is, one of the Star Trek writers got their hands on it. Apparently one of them heard the tardigrade story, perhaps someone who'd had a bit of biology in college (I'm guessing here), and got so excited that they turned it into a wildly implausible premise for an intergalactic space drive.

The idea of using horizontally transferred DNA for space travel is so nutty, so bad, that it's not even wrong. Even if tardigrades could absorb foreign DNA (they can't), how the heck is this supposed to give them the ability to tap into the (wildly implausible) intergalactic spore network? DNA that's been taken up through HGT isn't connected to the source any longer. This is no more plausible than asserting that people could connect to the mushroom network by eating a plate of mushrooms. And how would the space-traveling tardigrade take the entire ship with it? Are we supposed to assume it's creating some kind of mushroom-DNA field?

Star Trek has had faster-than-light warp drives for 50 years. Although physically implausible, warp drive isn't laughably ridiculous. The DASH drive is.

And now the entire series seems to be based on a combination of magic (an intergalactic mushroom network in subspace) and scientific errors (horizontal gene transfer by tardigrades).

I can't watch this nonsense. I'm willing to suspend disbelief for the sake of a good story (warp drive!), but I can't accept obviously bogus claims. I don't know how the Star Trek writers can get themselves out of this one, but if they don't, then Star Trek Discovery is finished. If they're reading this, here's my plea: ditch the DASH drive and find something to replace it–and for god's sake, hire a competent science consultant.

Better diagnosis of infections

This week I'm not posting an article here because I wrote a piece for BloombergView, the online magazine published by Bloomberg, the company founded by Michael Bloomberg. The article is titled "Make Way for Better Germ Tests." Check it out here.

A DNA Sequencing Breakthrough for Pregnant Women

DNA sequencing has made its way to the clinic in a dramatic new way: detecting chromosomal defects very early in pregnancy.  We've known for 25 years that traces of fetal DNA can be detected in a pregnant women's blood. But these traces are very small, and until now, we just didn't have the technology to detect an extra copy of a chromosome, where the DNA itself is otherwise normal.

Last week, in a study published in The New England Journal of Medicine, Diana Bianchi and colleagues showed how DNA sequencing can detect an extra copy of a chromosome with remarkable accuracy. This report heralds a new era in prenatal DNA testing.

First, some background: three copies of chromosome 21 causes Down syndrome, a genetic disease that causes intellectual disability and growth delays. Down syndrome is also called trisomy 21, where trisomy = 3 copies of a chromosome instead of the normal 2 copies. Much less common is Edwards syndrome, caused by three copies of chromosome 18. Edwards syndrome, or trisomy 18, has much more severe effects, with the vast majority of pregnancies not making it full term. Having an extra copy of any other chromosome almost always causes an early miscarriage. For many reasons, prospective parents want to know if a fetus carries any of these abnormalities.

The accuracy of the new test is remarkable. Out of 1914 young, healthy pregnant women, there were just 8 pregnancies where the fetus had an extra chromosome, and the test detected all 8. What was most impressive was its low false positive rate: in total, the new DNA-based test had just 9 false positives (for either chromosome 21 or chromosome 18 trisomy).  By contrast, the conventional screening test, which also identified all 8 true cases, produced 80 false positives, nearly 9 times as many as DNA sequencing.

Why does this matter? In most cases, women with a positive result on one of these tests will opt for amniocentesis ("amnio"), an invasive procedure where a doctor inserts a long needle directly into the womb and collects a sample of amniotic fluid. Amnio almost always gives a definitive answer about Down syndrome. With the conventional method, its false positive rate is so high that even with a positive test, over 95% of amnios will be negative, versus 55% with the new DNA sequencing test. Or to put it another way, as Bianci et al. wrote:

"if all women with positive results had .. decided to undergo an invasive procedure, there would have been a relative reduction of 89% in the number of diagnostic invasive procedures."

89% fewer invasive procedures is a huge reduction, not only in costs but in stress for the parents and risk to the baby (because amnio carries a small risk of miscarriage).

With DNA sequencing getting faster and cheaper every year, it might be surprising that we are only now seeing it used to detect trisomy. The difficulty with detecting an extra copy of a chromosome is that the DNA sequence itself is normal. If you sequence the genome, you won't find any mutations that indicate that the fetus has an extra chromosome copy. This is where the remarkable efficiency of next-generation sequencing comes in.

In a matter of hours, modern sequencing machines can sample millions of small fragments of DNA. We can use computational analysis to determine which fragments come from the fetus, and how many came from each chromosome. If any chromosome has three copies, we'll see a 50% increase in DNA from that chromosome. The power of sequencing lies in large numbers: because we can sequence many fragments from each chromosome, a 50% increase is easy to detect.

The method that Bianchi used to detect trisomy was published in 2011 by Amy Sehnert and colleagues from 2011, some of whom are contributors to the new NEJM study. [Side note: they use a software program called Bowtie, developed by my former student Ben Langmead, to do the analysis.] The method is likely to get even better over time, further reducing the false positive rate.

The American College of Obstetricians and Gynecologists has already recommended DNA testing for pregnant women at high risk of fetal aneuploidy (an extra chromosome). To be precise, they recommend that high-risk pregnant women be offered fetal DNA testing as an option, after they get genetic counseling. This new study, which was conducted in a low-risk population, shows that the benefits of prenatal DNA testing should offered to all women.

Another humanoid species walked the earth

[I'm on vacation, and this short post will appear while I'm away.]

One of the coolest scientific discoveries of the past few years was a small bone found in a remote region of Siberia.  The scientists who found it initially thought it was just an early human fossil, or else a Neanderthal fossil, but something about it looked a bit off.  It was just one small finger bone, not much to go on.

But DNA sequencing told a different tale.  The bone belonged to a female who was neither human nor Neanderthal, but something in between.  She and her kind appear to be closer to Neanderthals than to modern humans, but there is no doubt that she represents a new hominid species, one that died out only recently in evolutionary terms.  The evidence indicates that this previously unknown group, called the Denisovans after the cave in which the bone was found, actually interbred with humans.

The latest findings were published last fall in the journal Science, by a team led by Matthias Meyer and Svante Paabo.  With just one small, 75,000-year-old finger bone, they knew that extracting DNA would be a challenge.  Most of the DNA from ancient samples comes from bacteria and other creatures that have infiltrated the bone over the millenia.  But they were lucky in one respect: Siberia is cold, and has been for a very long time, which helps to preserve DNA.  Still they had to develop an entirely new method of extracting ancient DNA for this bone.

Meyer and colleagues extracted enough DNA to cover the entire genome of this ancient female.  They estimated that Denisovans and human diverged over 175,000 years ago.  They also discovered that modern Papuans contain vestiges of Denisovan DNA in their genomes, about 6%, suggesting that interbreeding occurred when humans were spreading across Asia.

Just this month, National Geographic's Jamie Shreeve published a feature article on the discovery, providing a fascinating look at how a single finger bone revealed a previously lost sister species.  (I highly recommend it, even for those who read the original Science article.) Now that we know what to look for, we might find more, and learn more, about these almost-humans from ancient Siberia.  And maybe we'll eventually figure out why they disappeared.

A final note: this discovery is yet another example of how evolution has shaped the history of life on this planet, but somehow I suspect the anti-evolution forces in the U.S. will find a way to deny it.

Supreme Court bungles the science in DNA patent decision

[This is slightly modified from my post 2 days ago at Forbes.]

The Supreme Court ruled this week that Myriad Genetics doesn't own your DNA after all.  Myriad holds patents on the BRCA1 and BRCA2 genes, which are linked to an increased risk of breast and ovarian cancer, and they charge exorbitant fees for their DNA diagnostic test of those genes.  As I've written before (such as this 2012 Clinical Pharmacology article), Myriad didn't invent the genes, and the patents should not have been granted.  So in large part the Supreme Court got it right.

But they got the science wrong, as any geneticist reading today's decision will realize immediately. In the very first paragraph, they make no less than three errors of fact.  First, they write:

"The nucleotides that code for amino acids are 'exons,' and those that do not are 'introns.' "

Not correct.  Here's the facts: when making DNA into a protein, the cell copies DNA into RNA.  Big chunks of the RNA are spliced out and discarded.  Those are "introns."  What remains is "exons."  That's it.  The nucleotides that code for amino acids are contained within the exons, but they are not the same thing. It's not unusual for 25% or even 50% of the nucleotides in the exons to be ignored when stringing together amino acids to make a protein.

Error number 2 comes next, when the Court writes:

"They [scientists] can also synthetically create exons-only strands of nucleotides known as composite DNA (cDNA)."

Wrong again.  cDNA stands for complementary DNA, because the DNA produced is the complement of the original strand. This means that each nucleotide is replaced with its complement: A and T are complementary, and C and G are complementary.  The court gets this right later on in the ruling.

Just after this, they write:

"cDNA contains only the exons that occur in DNA, omitting the intervening introns."

Ouch! Wrong again.  cDNA simply means a complementary copy of DNA, which doesn't have anything to do with exons.  If you make a cDNA from a mature messenger RNA transcript, then yes, it will contain only the exons.  But you can make cDNA from other parts of the genome, and from other types of RNA transcripts.

There are more errors further down in the decision. For example, they write that "Nucleotides that do not code for amino acids, in contrast, are known as 'introns.' "  This just compounds one of the errors above.  They also used the term "pre-RNA" instead of the correct term "pre-mRNA."  I could go on.

It's troubling that the highest court in the land can't get even the basic facts of molecular biology right when writing a decision that has such fundamental importance to genetic testing, the biotechnology industry, and health care.  I cannot pretend to know who they got to do their biology background research, but any genetics graduate student could have done far better.