My Skepticon talk: Skeptical Genetics

My talk from Skepticon is now online! If you ever wanted a quick and dirty summary of basic genetic concepts, now’s your chance. I try to address a lot of common misconceptions about genetics and address some of the shoddy ways genetics is portrayed by the media:

That was my first time giving that talk. From the Q&A and questions I got afterward, I certainly know what sort of stuff I need to add, subtract, or explain better. If there’s still anything you don’t quite get about genetics, feel free to leave a question in a comments.


  1. cmv says

    “How unique are you?”

    Oh, no. I’m looking forward to watching this, but you have to change that slide. You cannot be more or less unique.

  2. says

    Just watch the talk and enjoyed it greatly. I have a couple of comments. I may have misunderstood you, but did you say that cystic fibrosis was X-linked? That can’t be right…

    I was skeptical of what you said about heritability of autism and intelligence so I looked it up and found that what you said is correct. I had thought that heritability of intelligence was much lower although I can’t remember why I thought that. The only thing about that is that you might want to say IQ instead of intelligence since no one really thinks that IQ tests are perfect measures of intelligence.

    What you said about DNA in convicting criminals and how in the past it mostly tested for markers that vary more in people of European heritage was interesting. Do you know if this has led to any/many false convictions? Also, most people in the U.S. have mixed backgrounds. It seems like false positives in DNA tests might not be too much of an issue (although certainly any is something to worry about) here since most black people have a substantial amount of European ancestors as well as African. This may not be too much of an issue now that DNA testing is a lot more sophisticated than it used to be.

  3. Brian says

    You cannot be more or less unique.

    Words are allowed to have more than one meaning in English. Merriam-Webster’s 3rd definition for unique lists is as a synonym for unusual or extraordinary, and backs that up with a quote from J.D. Salinger, from 1950. The Cambridge Dictionary of American English defines unique as “being the only existing one of its type or, more generally, unusual or special in some way.” The American Heritage Dictionary notes that such usage (as a comparative instead of an absolute) is still considered informal by many grammarians, but is absolutely common in e.g. the language of advertising.

    In short, you’re free to restrict yourself to the more rigid meaning of unique, but you can’t really ask others to do so. That ship sailed decades ago.

  4. Daniel says

    Two things I noticed:

    – Please speak slower.

    – Jokes are ok, but please don’t laught at them, it seems lessens their impact.

    A good place to see great presenters (some even have humour) is

    Sorry for bringing the up only these two negative points, but I don’t know about genetics to see the great.

  5. Brian says

    I’d agree on the speaking slower part. But don’t laugh at your own jokes? That’s fine advice for a professional stand-up comedian, but I don’t think it really matters for an informal introduction to genome science.

  6. Screamer77 says

    I don’t think she’s speaking particularly fast, but I can see how this is very subjective and when you want to be clear it’s better to speak slower. I definitely don’t agree with the jokes suggestion. It’s not like she’s laughing all by herself, she’s laughing with the audience.

  7. BCskeptic says

    Thanks Jen, I really enjoyed your talk.

    So I understand that there is this super-long strand of DNA all coiled up in each cell, and that sections of DNA are genes, but what is the mechanism that that strand in the cell affects the cell…how does it interact with, I guess, the proteins in the cell?

  8. Milo Leraar says

    Hey Jen!

    I am assuming that you try your hardest to be a trans ally, so you should avoid statements like “All women have two X chromosomes” in the future. This is untrue in not only trans women, but also some intersex women.

    I didn’t have time to watch your whole video since it’s 2AM right now and I need to sleep! But I am very interested in watching it. I was just skipping around and heard that part.

    Have a good one!

  9. Esther says

    De-lurking to say thank you for a very enlightening talk. I lost you for the heritability part, though – that definition was unclear to me. As soon as you moved on to the next topic, it was all fine, but I still don’t get heritability…

  10. Svlad Cjelli says

    If you are assuming that a person is a single, homogenous thing.

    Does your car have a unique sticker? Have you configured the stereo uniquely? Is it the only surviving item of its model? Is it the only functional item of its model? Is it the only item of its model with a modern braking system? Is it the only item of its model outside of Uruguay? Is it the only car to make the Kessel Run in less than twelve parsecs?

  11. says

    The camera didn’t focus on the Wet Floor obelisk. What did it say?

    Genetics is weird to me, and I’d love to figure myself out. I am the only person in my family that I know of who has hazel eyes. None of my siblings have them. My parents don’t. My grandparents don’t. It’s weird and I’d love to know where I got them.

    And no, I’m not adopted cause I definitely look like my father (with some Native American features like my cheekbones and very dark hair.)

  12. Predator Handshake says

    Katherine, from what I can recall of my very limited formal education in genetics eye color is determined polygenetically. If I’m right about this it’s just that you happen to have the right combination of different genes that cause hazel eyes.

  13. says

    Hi Jen,
    I liked your talk. I wonder if, sometime in the future on this blog, you would look skeptically at some of the basic claims of standard genetics rather than just the obviously crazy claims of creationists or make-up marketers (though I enjoyed those parts of your talk!!!).

    For example, people often think that if within-group variation is greater than between-group variation, the groups are not strongly differentiated genetically. You used this myth in your talk, when you talked about human within- and between-group variation.

    When diversity is high, even two groups that have ABSOLUTELY NO alleles in common will have much greater within-group variation than between-group variation, and Fst or Gst between those groups will be close to zero. It is easy to see this by working some examples where within-group diversity is very high and the groups share no alleles.

    This myth was introduced to human genetics in the ’70s by Lewontin using entropy as the measure of diversity, and by Nei using heterozygosity as the measure of diversity, and is very widespread in the published literature, textbooks, and in talks. There are many more myths in standard pop gen, because of widespread misunderstanding the mathematics of diversity and differentiation.

    I hope you do a post on these kinds of myths. It is kind of amazing that such an apparently rigorous science like genetics can be so wrong about some of its fundamental concepts. It is even more amazing that it is so easy to disprove these myths in two minutes by doing simple examples. I think this is one of the most curious situations in the history of modern science.

  14. Mark says

    Nice talk! Please join the American Society of Human Genetics, and get involved/volunteer for their high school genetics education project (they usually do a session in the host city of the annual meeting – San Francisco next year- but have programs nation wide throughout the year). You are a natural

    Brief comment on warfarin: the poor uptake of genetic testing had little to do with physician trust, but rather timing. Physicians usually start patients on warfarin (coumadin) emergently after they have suffered a deep venous thrombosis (DVT) or pulmonary embolism. So the initial dose is guesstimated long before a genetic test result would return. Even as the turnaround time for cytochrome P450 and vitamin K genes reduced to 1/2 hour by a light cycler, having a PCR machine in every emergency room just didn’t make sense.

    The alternative is to test everybody in the population beforehand (e.g. the “23 and me” genomics approach) and have the information up front for the small percentage who suffer a DVT. Someday… but universal healthcare first!

  15. says

    You’re correct, cystic fibrosis is NOT X-linked. If I said that, I misspoke. This is why you should get sleep before your talks…

  16. says

    I actually noticed that one as well when Jen was talking about Barr bodies, although I was thinking more of men and women who are XXY or other variants.

    I assumed she didn’t really want to get into how you never want to have more than one of any type of chromosome because it causes serious problems, usually fatal, unlike Down’s Syndrome. It’s hard enough to talk about genome inheritance when everything goes how it’s supposed to, let alone talking about all the ways that things can get messed up.

  17. says

    I have to give it to you. I was running in ADD mode, watching a Mythbusters episode about Ninjas while looking at blogs at the same time, and I started watching your talk. Well, I watched the whole thing! Not only did you overcome my ADD phase, you also won over Mythbusters!

    Very nice talk btw. I learned quite a bit!

  18. Sarah B says

    Are you going to be really disappointed to find out that there have been three articles published (including a letter to Nature) about the inheritance of magic in the Harry Potter universe? I was. :D

    This is why I wanted to write about the zombie virus – then I found out someone had already used it as a means of studying disease models. :)

  19. Ashton says

    I’m not sure that you did say that. It’s just that you mentioned it at the same time that you were talking about x-linked genetic. It sounded implied.

  20. says

    Thanks! I enjoyed it. I’d like to put in a vote FOR your talking speed (fast enough — not boring — yay!) AND your jokes & laughter. You seemed relaxed and comfortable because of it.

  21. Ted Powell says

    One can keep the pedants (including me) at bay by writing, “How distinctive are you?” It’s a good word, matches the intended meaning, and avoids mentally sidetracking readers from genetics to English usage.

  22. Ted Powell says

    Could it be that Down’s Syndrome is an exception to the general fatality of trisomy partly because chromosome 21 is a very small chromosome—lower probability of “important” stuff being on it?

  23. ottod says

    I don’t understand why you had a picture of P. Z Myers on that slide. And why was he wearing that funny, pointed hat?

  24. Holly says

    You discussed DNA between siblings but didn’t mention anything about identical, or monozygotic, twins. I’m sure it’s a fairly simple answer but I just haven’t heard much about it. How similar is their DNA?

  25. lpetrich says

    If you ever get into eugenics, I suggest explaining that it’s artificial selection, and that one of the first advocates lived nearly 2400 years ago — Plato. He proposed that his Republic’s rulers marry people at random, by lot, or so it would seem. They would rig the lots using eugenics principles, like what domestic-animal breeders do. Yes, he made that analogy.

    You could also mention royal families’ genetics, like Queen Victoria being a hemophilia carrier, some female descendants also being carriers, and some male descendants having the disease. Also Habsburg jaw, in that centuries-old royal family.

  26. Sameer says

    Hi Jen,

    Really liked your talk. I thought the question about why you think humans are 99.9% the same genetically but siblings on average being only 50% similar was really interesting. Can you post something on it explaining it more on the blog?

  27. Don C says

    Hi Jen. Been reading your blog for 2 or 3 yrs now…always impressed w your intellect, knowledge and viewpoint….but now that I’ve seen you on video…I have to say you’re the full package….because now I see you are also confident, good speaker, engaging. entertaining, lovely…and probably someone whose friends love to hang out with you. Keep up the good work and the well-crafted messages on all the topics we know you like to write about. Thx

  28. says

    After study a several blog posts on your web site now, and I truly like your way of blogging. I bookmarked it for you to my bookmark website list and will be checking back soon. Pls check out my web site as well and allow me to know what you believe.

  29. Justin says

    Great presentation! Although at my school you would be convicted in honor court and suspended for not citing sources under photos you used :). I also have one personal request, please refer to “doctors” as physicians from now on in the interest of preventing misconceptions. It’s a pet peeve of mine and a lot of of my pharmacy, dentistry and research colleagues. You know first-hand that there is more than one type of person than can have Dr. in front of their name lol. Again, great presentation I’ll bookmark you.

    Justin Robinette
    Pharm.D. Candidate
    UMaryland Baltimore

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