Lessons for human genetics from genetic screens in model organisms

Why did the axon cross the midline? That seems like a simple enough biological problem to solve. In the developing nervous system, especially in the anatomically simple spinal cord, some nerve cells send a slender nerve fibre (called an axon) across the midline of the nervous system to connect to cells on the other side. The projections of other neurons are restricted to the same side as their own cell bodies. The connections between the two sides are crucial in coordinating movement of the two sides of the body. But, more importantly for this discussion, this system is simple enough to be genetically tractable – at least it seems so.
When I arrived as a graduate student in the lab of Corey Goodman at the University of California at Berkeley, his group had just carried out a genetic screen in fruit flies to try and understand how this developmental decision was controlled. Flies have an equivalent of a spinal cord, called the ventral nerve cord, and Corey and his colleagues had spent m…

Panpsychism – not even wrong. Or is it?


“Like father, like son”: Testing folk beliefs about heredity in the arena of assisted reproduction.

“The apple doesn’t fall far from the tree”. “Chip off the old block”. “Cut from the same cloth”. “Black cat, black kitten”. “Chickens don’t make ducks”. “He didn’t lick it off the stones”. “It’s not from the wind she got it”. “She comes by it honestly”.
Every culture seems to have its own phrases describing the power of heredity – not just for physical traits, but also for behavioural ones. (Those last three are peculiar to Ireland, I think). This folk wisdom, accumulated from centuries of observation of human behaviour, seems to reflect a widespread belief that genetic effects on behaviour and personality are strong, indeed dominant over effects of upbringing.
(Image credit:
Of course, folk wisdom can be wrong. And old folk sayings may not reflect current thinking – perhaps people’s opinions on the subject have changed. Indeed, if you were to take academic discourse on the subject as a barometer of views of the general public, y…

What are the Laws of Biology?

The reductionist perspective on biology is that it all boils down to physics eventually. That anything that is happening in a living organism can be fully accounted for by an explanation at the level of matter in motion – atoms and molecules moving, exerting forces on each other, bumping into each other, exchanging energy with each other. And, from one vantage point, that is absolutely true – there’s no magic in there, no mystical vital essence – it’s clearly all physical stuff controlled by physical laws.
But that perspective does not provide a sufficient explanation of life. While living things obey the laws of physics, one cannot deduce either their existence or their behaviour from those laws alone. There are some other factors at work – higher-order principles of design and architecture of complex systems, especially ones that are either designed or evolved to produce purposeful behaviour. Living systems are for something – ultimately, they are for replicating themselves, but the…