A recently posted YouTube video tries to make the case that you were lied to about genetics. I'll get to than in a little while but first let me summarize what I was taught in a university genetics class in 1965.
Like many of you, I was taught the rudiments of Mendelian genetics in high school. This view was emphasized in my university course where we learned about Mendel's laws of inheritance in diploid species. I also learned about population genetics and exceptions to the standard rules governing the segregation of alleles. We covered 'phage and bacterial genetics where Mendel's laws mostly don't apply and we learned about sex-linked alleles that show more complicated inheritance.
There are hundreds of excellent examples showing a direct link between genotype and phenotype but there are also many examples where this connection is obscure, especially in complex multicellular organisms such as fruit flies, plants, mice, and humans. For example, there's no obvious reason why a deficiency in a starch branching enzyme should cause wrinked peas [Biochemist Gregor Mendel Studied Starch Synthesis]. And there's no obvious reason why mutations in the same gene in humans causes a liver disease in children that's usually fatal (Anderson disease) [Glycogen Storage Diseases]. The mutant alleles still segregate according to Mendelian genetics.
Genes interact to form networks and some of these networks are complicated. We usually teach simple examples such as how suppressor genes can mitigate the effect of stop mutations in bacteria. There are more complicated examples such as the large number of alleles and different genes that affect eye color in humans [The Genetics of Eye Color]. When the number of different loci is low, you can still work out the Mendelian probabilities using Punnett Squares but in some cases there are just too many loci with low penetrance.
In order to make his case, he focuses on the complicated examples of multigene inheritance in humans. The interesting part of the video is his version of Waddington's genetic landscape and his toy model illustrating the concept. I think he's dead wrong about the death of Mendelian genetics but it's still worth watching the video.
21 comments :
This whole "you were lied to" trend is one of the most annoying and frustrating aspects of social media and society in general of late. At worst, information taught in the past may have been expanded or updated, but were people actually lied to?
As Larry notes, the popular science media seem to need to tout each science discovery as revolutionary and overthrowing all previous knowledge. Headlines like "Scientists astonished as new study [of the number of hairs on the ass of the wombat] gives amazing results.". Of course university press releases don't do much to fight this ...
The entire "You were lied to" format is efficient clickbait, used in politics to generate mistrust of democratic institutions, and used in creationism, often by the same people, to generate mistrust in the whole of evolutionary and deep time science
Hi Joe, how are you ? I previously inboxed you on facebook and you never responded actually I want to clarify something. In my country Pakistan , I see a lot of creationists misuse your advisor Dick Lewontin's qoute to set their own agenda. Now I do not know that in which context Lewontin said so, so you are the best person who can clarify what actually Lewontin tried to say in the given qoute. Thanks in advance ! Here's the qoute :
.‘We take the side of science in spite of the patent absurdity of some of its constructs, in spite of its failure to fulfill many of its extravagant promises of health and life, in spite of the tolerance of the scientific community for unsubstantiated just-so stories, because we have a prior commitment, a commitment to materialism. It is not that the methods and institutions of science somehow compel us to accept a material explanation of the phenomenal world, but, on the contrary, that we are forced by our a priori adherence to material causes to create an apparatus of investigation and a set of concepts that produce material explanations, no matter how counter-intuitive, no matter how mystifying to the uninitiated. Moreover, that materialism is an absolute, for we cannot allow a Divine Foot in the door.’
Jake Brown's video refers to the works of historian, Gregory Radick, who has recently summarized his views in Disputed Inheritance. The Battle over Mendel and the Future of Biology (2023. Univ. Chicago Press). Celebrating the bicentennial of Mendel's birth, in 2022 there appeared the second edition of Cock and Forsdyke's Treasure Your Exceptions. The Science and Life of William Bateson (Springer, New York). Here, Bateson - who coined much of the genetic terminology we use today - explains a key point that Jake Brown makes, namely that Mendel began by selecting lines of peas that "bred true."
A century later, the research principle that interpretating data is likely to be easier by either making the studied system simple or choosing a simple one at the outset. This became abundantly evident with the increased entry of physicists into biology. Thus, studies of the viruses that infect bacteria created an important grounding for the later DNA studies of Watson and Crick.
@Mohammed Abdullah, I do not read Facebook Messages. I do read emails; my email address will be found at my Github repository, at felsenst.github.io, in my C.V. there. Lewontin's point is made clear by the next sentence of his statement: "The eminent Kant scholar Lewis Beck used to say that anyone who could believe in God could believe in anything. To appeal to an omnipotent deity is to allow that at any moment the regularities of nature may be ruptured, that miracles may happen." In effect he is saying that supernatural mechanisms are unusable because they do not lead to any prediction, that they do not rule out anything. People who quote Lewontin's statement as a Damning Admission often leave out those additional sentences.
And, in agreement with Larry, the idea that one gene leads to one phenotype has long been discredited. I mean long. Like, more than 100 years ago. Not just before Watson and Crick 1953. I mean in discredited in the 1910s. Discredited before 1920, when people began to understand that color mutants in mice also had neurological side effects. By 1918, Fisher's great quantitative genetics paper showed that correlations between relatives in measurable traits were consistent with Mendelian inheritance of the individual loci that contributed to those traits. I somehow doubt that genetics courses have ignored all these discoveries.
I see that the word "pleiotropy" dates to 1910.
For discussion of "pleiotropy" and "epistasis" see Mackay & Anholt (Nat. Rev. Genetics 25:639-57). They note the latter term was coined by William Bateson in 1907 (ref. 149).
This video may be influenced by this new book: Kostas Kampourakis (2024). How We Get Mendel Wrong, and Why It Matters: Challenging the narrative of Mendelian genetics. CRC Press, 1-226.
While the book has a lot of good information, the last chapter seems to go off the rails and go all the way to the idea that it is positively misleading to teach Mendelian genetics, Punnett Squares, etc. to first-year biology students.
e.g., 2nd to last page: "I therefore propose a shift in education toward designing school curricula and teaching materials that present the role of genes in their developmental contexts and for education research to investigate how students can understand this. If the aim is to educate scientifically literate citizens, then we should refrain from teaching students about genes that control or determine traits and give them instead a sense of the complexity of genomes. Mendel's work cannot provide useful lessons for today's genetics, and the oversimplistic accounts of Mendelian inheritance and the Punnett squares do not accurately represent the phenomena of heredity. This is why we had better drop Mendelian genetics altogether from the genetics curriculum: it is simply inaccurate." (p. 206)
I think this is rather a lot like recommending we drop the Periodic Table from chemistry class, because most things we see in nature are made of multiple kinds of atoms. I.e., it's nuts!
(that anon comment was me - Nick M.)
Mohammed Abdullah, it may not be obvious (it was not obvious to me until a friend pointed out) but if you take the quotation in context, you will see that it is not what Lewontin believed, but on the contrary his summary of Sagan's position in Demon Haunted World, which he considered facile
So to sort of summarize Lewontin's point in a succinct way: Science isn't perfect at all, but it's still much better than the alternatives.
Verrry interrrestink! Will try to get a copy of Lewontin's NYRB review and check this. Thanks for pointing this out.
I propose a shift in education toward designing school curricula and teaching materials that present the role of gravity in a relativistic context and for education research to investigate how students can understand this. If the aim is to educate scientifically literate citizens, then we should refrain from teaching students about gravity that operates in a fixed Euclidean spacetime and give them instead a sense of the complexity of the interaction between gravity and spacetime. Newton's work cannot provide useful lessons for today's physicists, and the oversimplistic accounts of the inverse square law and Kepler's laws of planetary motion do not accurately represent the phenomena of planetary orbits. This is why we had better drop the Newtonian model altogether from the physics curriculum: it is simply inaccurate.
I have now seen Lewontin's "materialism" statement in the context of the full article. It seems to me he is describing the situation scientists find themselves in, rather than describing Sagan's position with which he disagrees.
Mohammed Abdullah, The quote is from new York Review of Books, Volume 44, Number 1 · January 9, 1997, Billions and Billions of Demons: a book review of a book by Carl Sagan.
The ful quote is:
"ur willingness to accept scientific claims that are against common sense is the key to an understanding of the real struggle between science and the supernatural. We take the side of science in spite of the patent absurdity of some of its constructs, in spite of its failure to fulfill many of its extravagant promises of health and life, in spite of the tolerance of the scientific community for unsubstantiated just-so stories, because we have a prior commitment, a commitment to materialism. It is not that the methods and institutions of science somehow compel us to accept a material explanation of the phenomenal world, but, on the contrary, that we are forced by our a priori adherence to material causes to create an apparatus of investigation and a set of concepts that produce material explanations, no matter how counter-intuitive, no matter how mystifying to the uninitiated. Moreover, that materialism is absolute, for we cannot allow a Divine Foot in the door. The eminent Kant scholar Lewis Beck used to say that anyone who could believe in God could believe in anything. To appeal to an omnipotent deity is to allow that at any moment the regularities of nature may be ruptured, that miracles may happen."
The important point is in the last sentence, the sentence creationists always omit: "To appeal to an omnipotent deity is to allow that at any moment the regularities of nature may be ruptured, that miracles may happen." Science cannot funnction if at any moment 'the regularities of nature' can be broken.
The quote is a creationist favourite, as it is used to argue a philosophical adherence to materialism in science, rather than a practical materialism of methods.
I think that what we are dealing here, in Jake Brown's video and in Kostas Kampourakis's book, is postmodernism. Note that Kampourakis describes our picture of inheritance as a "narrative". Extreme postmodernism regards everything as a "narrative", all equally dubious, ignoring the interaction with the real world that gives science direction towards better and better descriptions of the world. In the fully-postmodern view, any flaw in the scientist's social or political view always "calls into question" the results. Along those lines I agree with Nick M that we must describe all possible complications. Astronomy must drop all that stuff about perfect spheres moving in elliptical orbits about bigger, heavier perfect spheres. Let's emphasize to students that planets have irregular surfaces and then let's insist we model that.
https://youtu.be/Gddkc5Snq3I
Almost all inheritance is multigenic & almost every gene is pleiotropic, with some few exceptions sorting according to high school Punnet Squares
@Anonymous says, "Almost all inheritance is multigenic & almost every gene is pleiotropic, with some few exceptions sorting according to high school Punnet Squares"
Really? I worked for years with genes in bacteriophage T4 and E. coli and I didn't notice that all inheritance was multigenic and every gene is pleiotropic. On the other hand, I did notice that none of those genes sorted according to a Punnett Square.
When it comes to humans, your perspective depends very much on what you are studying. If you are studying complex characters like height and intelligence then you will be interested in multigenic inheritance.
But if you are studying the effects of various alleles on the activity of enzymes in glycogen metabolism, then the sorting of single alleles (Punnett Squares) is important.
Glycogen Storage Diseases
It's a little bit naive to trash an entire discipline just because the only things you are interested in are the genetics of complex systems in humans.
Post a Comment