The same process works going forward in time; in essence every one of us who has children and whose line does not go extinct is suspended at the center of an immense genetic hourglass. Just as we are descended from most of the people alive on the planet a few thousand years ago, several thousand years hence each of us will be an ancestor of the entire human race—or of no one at all.
There’s a famous old anecdote about Charlemagne that’s been used for ages to explain how interconnected we are among our biological pasts. It has been said that everyone of European ancestry is related to Charlemagne, the great King of the Franks, born in 742 AD. If you’re European, you’re royalty. How is that possible?
I’ll tell you another tidbit first: Not only do all Europeans share Charlemagne as an ancestor, they share everyone alive at the same time as Charlemagne as an ancestor. Everyone who had kids, anyway. Let me explain:
Everyone alive has two biological parents. They each have two parents themselves, for a total of four grandparents. For x number of generations that you travel back in time, you have 2^x direct grandparents of increasing separation. Extrapolate that back to Charlie’s time, and you’d need 1 trillion grandparents to cover all your ancestral bases. Michael from Vsauce did a video about it. Since that’s far more people than have ever been alive, we need to engage some incest to solve the problem. Not banjo-applesauce incest, just a bit of redrawing our family trees into family webs.
Somewhere, far enough back in the web of grandparents, we will find a person whose lines connect to every single person who comes after them. That zig-zagged trail of shared genetic history ends surprisingly recently (for Euros, again): A common European ancestor around 1400 AD. Go a bit farther, and we find a common Earthling ancestor around 3,000 BC. It’s neat stuff. But it’s all based in mathematical models, not real genetic data.
Until now. USC and UC Davis researchers Peter Ralph and Graham Coop have surveyed the genomes of 2,257 Europeans in order to put some real data behind those models. Because of the random shuffling of chromosome fragments that created your father’s sperm and your mother’s egg, you, your siblings and your cousins all share varying chunks of DNA. People who are more closely related share more of these chunks. Depending on how many chunks are shared between two people, we can calculate their approximate relation to each other. Using 2 million shared sequences and a lot of math, they proved the mathematical models correct. Turkish people are more related to other Turks than to someone from Portugal, but they are related enough that, not only do they share one common ancestor a few hundred years ago, but they share every ancestor if you go back a mere thousand years. The models guessed that a long time ago, but now we have the data to prove it.It’s likely that these patterns extend to other regions of Earth, although the numbers might be slightly (but not that) different.
Next time someone in your neck of the ethnic woods points out a famous relative or claims blue-blood descent, remind them that they aren’t so special. All street-sweepers are royalty, all nobles are peasants, and we are all Kings and Queens.
In ants and bees, there are no sex chromosomes. Instead, sex is determined by whether or not an egg was fertilized. If the egg isn’t fertilized, the offspring is male. If the egg is fertilized, it’s female. So male ants have no fathers, and they have half as many chromosomes as females. Poor little things.
I’ve always maintained that its not the number of chromosomes that matters, but rather how you use them.
The Science of Hair Loss and Balding by the AsapSCIENCE guys. Alopeciate it if you’d watch this video.
It’s not as simple as just your maternal grandfather, but that’s part of it. Scientists have identified one of the key proteins (and its target) that make men go bald. And did you know that the major commercial treatments for androgenetic alopecia (male-pattern baldness) were found by accident? Rogaine was a blood pressure drug and Propecia was for prostate enlargement!
I’m pretty confident that these flowing blond locks of mine are gonna stick around for a while … knock on (genetic) wood.
How Mendel’s Pea Plants Helped Us Understand Genetics (now with working video!)
TED Ed takes a look back at Gregor the Monk’s pioneering genetics experiments featuring the humble pea plant. When you remember that he figured all of this out before we had even discovered DNA or the molecular idea of a gene, it’s even more amazing.
That heterozygote dance looks like fun.
Previously: Awesome vintage illustrations of Mendelian genetic patterns featuring fluffy mice!
Sculpting a Catalogue of Apples
Apples, at least as we know them, are a freakshow born of agricultural genetics. While wild apples readily grow from seeds, perhaps every single variety we buy in stores is produced by grafting.
With more than 7,500 wild varieties, apples have incredible genetic diversity. This is how we’ve been able to develop so many variations of size, sweetness, texture and color. The side effect is that many apple varieties are such Frankenstein monsters that they literally can’t grow from seeds. Combine that with the complicated way that apples pollinate, and you’ve got a recipe for a clone army in an orchard.
This is great for farmers, because you get a consistent product, but bad for apples, because many of the wild varieties could be lost or forgotten. And should some pest, parasite or blight start attacking our genetically-engineered superfruits, we’re going to want those wild genes around to call on to save the day. It’s diversity that makes a population strong.
That’s why I love this project so much. It’s an archive of apple varieties using ceramic sculpture! So cool.
If you’d like to learn more about the history of the humble apple, read The Botany of Desire by Michael Pollan. Great book for foodies and science fans alike. If you want to get super-sciencey, here’s a cool paper in PLOS Genetics.
More via theatlantic:
In its original home, near Almaty in Kazakhstan, the apple can be the size of a cherry or a grapefruit. It can be mushy or so hard it will chip teeth. It can be purple- or pink-fleshed with green, orange, or white skin. It can be sickly sweet, battery-acid sour, or taste like a banana. Preserving this biodiversity can become a massive project, in life and art.
See more. [Images: Jessica Rath]
Dominant vs. Recessive Alleles: Cracking the Case
Alex Dainis turns an episode of her YouTube show Bite Sci-zed into a film noir detective story. Gumshoe Alex gives femme fatale Alex a simple lesson in dominant and recessive genes to help crack the case of a maybe-affair.
Most traits in humans are not this simple (just like eye color isn’t actually this black and white, I mean blue and brown), but rather are caused by several genes and their combined influence. Still there are a few characteristics which show a simple dominant/recessive relationship, although they may still be caused my more than one gene:
- Widow’s peak in one’s hair (dominant)
- Dimples (dominant)
- Cleft chin (dominant)
- Unattached earlobes (dominant)
- Straight thumbs (dominant)
- Longer second toe than big toe (dominant)
Ah, Mendel. You brilliant monk. This is a beautiful example of the (optimal) pattern seen when you cross two organisms with a mixture of dominant (black/short hair) and recessive (white/long hair) genes, also known by the mouthful “dihybrid cross”. You can dig into it a little more here.
Coming of Phage
Everything you’ve been taught about phage is wrong. Well, maybe not everything. Heck, maybe you’ve never been taught anything about phage in the first place! But if you’ve ever encountered a story about this family of bacteria-infecting viruses, I’m willing to bet it included a picture much like this:
That geometric lunar lander is the standard illustration of phage such as T7. It looks exotic and alien, a freakish example of biological symmetry, but it’s pretty true to the actual biology: The icosahedral protein head, the protruding neck that it uses to pierce the membrane of its victim so that it can inject its genetic material … and the legs.
Wait a sec, those legs need revising. Some really cool new research by Ian Molineux (who taught my graduate school molecular bio class, btw) says that all those “legs-out”, moon lander drawings of phage probably aren’t right.
In the video above you see that, according to the electron imagery they report in their Science paper, those legs stay tucked up next to the body for most of the free-floating life of the phage. It sort of drags one or two along, waiting to hook onto an appropriate bacterium that it can infect, at which point it extends the rest of the legs to go into full infection mode. To give you an idea of how hard this was to observe, a single phage is only around 20-30 nanometers wide, which means you could fit about 4,000 of them across the width of a single human hair!
It might seem like a small, ho-hum tidbit of research at first, since who really cares about a virus that infects bacteria? But phage are incredibly important. Phage have driven a great deal of the evolution of life on Earth. They are vehicles of gene swapping that have allowed genomes to expand and become more complex. They are veterans of 70+ years of biology research, from back when we first identified DNA as a genetic material to today’s exotic synthetic biology applications. A great deal of what we know about molecular genetics is because of these little guys, and we’re still making the most basic discoveries as to how they function.
Never let anyone tell you that there’s nothing left to discover! We have scarcely begun to fill in the colors, even for the most basic parts of biology’s palette.
Prenatal medical testing has long been a balance of risk with information. Submit yourself to tests and you can find out about the genetic makeup of your future child, but risk miscarriage and other complications. Omit the tests, and a pregnancy is safer, its outcome uncertain.
That’s how it used to be, anyway. Now, genetic tests are becoming so cheap and non-invasive that they could become as routine as an ultrasound. DNA from the fetus is known to float freely in the mother’s blood and can be drawn in seconds, to be later analyzed for things like Down syndrome.
What will this mean for parents who discover birth defects or diseases in their unborn children? It’s impossible to know precisely who a child will become, but a world in which parents are informed of their baby’s genetics just weeks after conception brings with it a lot of ethical dilemmas.
Erin Biba analyzes this in one of the most interesting medical articles I’ve read in a long time, at Wired Science.