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Category Archive: Development

Mar 25 2014

Epigenetics ain’t magic

I just got a notice of an Epigenetics Conference in Portland, Oregon. It made me cringe. It’s infuriating because epigenetics is actually a very important concept in development, but there’s this terrible misperception among the public that it’s a magical shortcut for evolution. I was also a bit primed for it by the mention of …

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Mar 12 2014

An atheist can be pro-life only by lying about the science

Hemant Mehta let an anti-choice atheist romp about and make her secular pro-life argument, but since he thinks it’s important to give a forum to bullshit but doesn’t think it’s important enough to criticize, I guess I have to. It’s by Kristine Kruszelnicki, president of Pro-Life Humanist, and we’ve dealt with her before; she’s the …

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Mar 11 2014

Pathways to sex

The molecular and genetic events in mammalian sex determination. The bipotential genital ridge is established by genes including Sf1 and Wt1, the early expression of which might also initiate that of Sox9 in both sexes. b-catenin can begin to accumulate as a response to Rspo1–Wnt4 signaling at this stage. In XX supporting cell precursors, b-catenin levels could accumulate sufficiently to repress SOX9 activity, either through direct protein interactions leading to mutual destruction, as seen during cartilage development, or by a direct effect on Sox9 transcription. However, in XY supporting cell precursors, increasing levels of SF1 activate Sry expression and then SRY, together with SF1, boosts Sox9 expression. Once SOX9 levels reach a critical threshold, several positive regulatory loops are initiated, including autoregulation of its own expression and formation of feed-forward loops via FGF9 or PGD2 signaling. If SRY activity is weak, low or late, it fails to boost Sox9 expression before b-catenin levels accumulate sufficiently to shut it down. At later stages, FOXL2 increases, which might help, perhaps in concert with ERs, to maintain granulosa (follicle) cell differentiation by repressing Sox9 expression. In the testis, SOX9 promotes the testis pathway, including Amh activation, and it also probably represses ovarian genes, including Wnt4 and Foxl2. However, any mechanism that increases Sox9 expression sufficiently will trigger Sertoli cell development, even in the absence of SRY.

I was talking about sex and nothing but sex all last week in genetics, which is far less titillating than it sounds. My focus was entirely on operational genetics, that is, how autosomal inheritance vs inheritance of factors on sex chromosomes differ, and I only hinted at how sex is not inherited as a simple …

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Dec 07 2013

The reification of the gene

Razib Khan poked me on twitter yesterday on the topic of David Dobbs’ controversial article, which I’ve already discussed (I liked it). I’m in the minority here; Jerry Coyne has two rebuttals, and Richard Dawkins himself has replied. There has also been a lot of pushback in the comments here. I think they all miss …

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Dec 03 2013

Higher order thinking

The one thing you must read today is David Dobbs’ Die, Selfish Gene, Die. It’s good to see genetic accommodation getting more attention, but I’m already seeing pushback from people who don’t quite get the concept, and think it’s some kind of Lamarckian heresy. It’s maybe a bit much to ask that the gene-centric view …

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Nov 22 2013

Sexy T-rex meets lecherous creationist

Charlie Stross has written a story, A Bird in Hand, which rather pushes a few boundaries. It’s about dinosaurs and sodomy, as the author’s backstory explains. And as everyone knows, every story is improved by adding one or the other of dinosaurs and sodomy, so it can’t help but be even better if you add …

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Oct 26 2013

How to make a funny-looking mouse

Attanasio-face-enhancers-9

I’m going to tell you about a paper that was brought to my attention by some poor science journalism, so first I have to complain about the article in the Guardian. Bear with me. This is dreadfully misleading. Though everybody’s face is unique, the actual differences are relatively subtle. What distinguishes us is the exact …

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Aug 29 2013

Cloning brains with Science

organoid_method

While we’ve been waiting and waiting for the physicists to get their act together and deliver on Mr Fusion home energy sources and flying cars, the biologists have been making great progress on the kinds of things that turn biologists on. The latest development: growing tiny little human brains in a bucket. Only let’s not …

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Aug 22 2013

Hamza Tzortzis can learn

Tzortzis has learned that claiming miraculous knowledge in the Qu’ran has “become an intellectual embarrassment for Muslim apologists”. Progress! Regrettably, the scientific miracles narrative has become an intellectual embarrassment for Muslim apologists, including myself. A few years ago I took some activists to Ireland to engage with the audience and speakers at the World Atheist …

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Jul 18 2013

Spontaneous abortion explosion

Now that we’re regularly getting small numbers of eggs and embryos every day, we thought we’d test out all the other gear by making an extended timelapse video, letting it run overnight. Unfortunately, in the wee hours of the morning, God apparently struck and slaughtered the little baby fish in its chorion, and embryo went …

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