Children are delighted by living things that most adults think are icky or mundane. Last spring my daughter Lucy, now age 6, found a large earthworm and named it Cinderella. She played with it for hours. Not a week later my son Josiah, 4, caught a big brown toad in our backyard and squealed repeatedly, “He’s adorable!” (Not everyone would pick that adjective, but I agreed.) They fixate on the fish tank at the dentist’s office or our family’s ant farm, taking in every detail and pestering me with a steady stream of questions.
Some of the questions they ask are profound. We were almost to school the other day when Lucy asked, “Is there any number bigger than infinity?” and then, “Is God bigger than infinity?” I paused, breathless with parental joy, before I responded. Continue reading →
I am an ex-cell biologist. Whilst I was a PhD student, it felt like cells were involved in every aspect of my life. I would grow cells, study cells, read about cells, spin them in centrifuges, look at them down a microscope, and visit them at 2am to take timepoints for particularly gruelling experiments. When I spoke to my relatives, the question ‘How are you?’ was often followed by: ‘How are your cells behaving?’. Continue reading →
This is the message that developmental biologist Jeff Hardin tries to get across to his students. Hardin constantly sees beauty in his work, so I thought I would spend some time explaining what he does. (Part 1 here, part 2 here, part 3 here.)
One of the best tools for studying development is the tiny roundworm C.elegans, which must be one of the most studied organisms in the world. Adult humans have around 50 trillion cells in their bodies, but human development is so complex and our bodies are so large and vary so much in size, that estimates vary from 10 to 100 trillion. C.elegans, on the other hand, is a relatively simple organism with about 1,000 cells.
One of the most striking (and useful) things about C. elegans is the ‘invariant lineage’ of its cells. As the embryo grows, development proceeds along a minutely prescribed pattern. A cell in the growing embryo replicates its DNA and divides in two. The ‘daughter cell’ will now follow instructions, either keeping the character of its parent or developing a new trait to form part of a different tissue. Each new cell has its fate mapped out in advance, so there is no room for teenage rebellion among the cells of the C. elegans embryo.
The other useful thing about this worm is its complete transparency, which has allowed biologists to trace the lineage of all 959 of its cells*, including the 131 cells that died along the way.
959. The life of a small organism can be completely prescribed: hatch, grow, moult four times, then mate. Most C. elegans adults are hermaphrodites – they make sperm, then switch to making eggs, and fertilise themselves. One could find this cycle depressing, but that’s not the take-home message for Hardin.
Biologists always seem to find their chosen organism beautiful, perhaps because they have come to appreciate its features in great detail. It certainly helps if you find beautiful the thing that you spend most of your days staring at. Being able to understand an organism in such detail is beautiful in itself. And the elegance of an animal that is so tiny and yet so detailed is astonishing. Long gone are the days when cells were thought to be homogenous, gelatinous blobs.
The world we inhabit is highly ordered and that order brings complexity. Creatures in some way make themselves, and reproduction is the best example of our being granted some part in the creative process. Even if we don’t completely understand the details, we get to ‘make’ whole new living things – worms on a Petri dish, geranium cuttings, kittens, children…
* Excluding the gametes, which have variable cell numbersIf you want to know more about C. elegans, you can read to your heart’s content in this online text book, http://www.wormbook.org, to which Jeff Hardin has contributed a chapter on epidermal morphogenesis.