If humans have an arch enemy, it might well be the tiny, blood-borne parasite Plasmodium falciparum. This nasty beast causes most of the malaria in sub-Saharan Africa and, together with its cousins, in many tropical zones throughout the world. It kills huge numbers of children every year, and constantly cycles through the bloodstreams of its many survivors. It has been with us since our explosive migration out of east Africa, and in fact many genetic diseases (including sickle-cell aneamia and thalassemias) are tolerated by human populations because they confer an advantage against this nasty parasite.
The humble fruit fly – Drosophila melanogaster, to be specific – has played a central role in the history of genetics and molecular biology and continues to be important in research.
Championed by the legendary Thomas Morgan at the start of the 20th Century, Drosophila provided a practical foundation for genetics – long before the discovery of DNA as vehicle for passing down heritable information through generations. Morgan and colleagues developed the concepts of ‘gene’ and ‘linkage’, and so we have ‘Morgans’ (and more commonly, centi-Morgans, cM) as the basic units of genetic maps.
In the early 90s Svante Paabo, a charismatic, energetic innovator, made a bold proposal: that to study human origins one would do well to sequence the DNA of ancient hominids, in particular those species which had gone extinct. After all, DNA could be detected in their bones, provided they were not too old and kept dry and cold.
On the second day of christmas, my true love sent to me: The C. elegans (worm) genome. The lowly nematode worm is probably the “newest” widespread model organism, developed by Sydney Brenner and colleagues in the 1960s at the Laboratory for Molecular Biology (LMB) in Cambridge as something between the complexity of fly and the simplicity of yeast.
It was an inspired choice: you could keep the worm in the laboratory easily (it eats a lawn of bacteria, very often E. coli), and setting up crosses was easy and remarkably (and this shows how lucky Sydney is), it has completely stereotypical development. Every adult C. elegans worm has an identical number of cells (John Sulston was one of the key people to work this out who would later lead the worm and genome project). It is as if every cell has a name, with one tree providing the single way of going from a genome to a collection of cells.
Inspired by a very boring train stoppage last year, I am going to add, one a day, to this of great / interesting genomes until christmas day.
On the first day of christmas, my true love sent to me:
Escherichia coli and its associated phages. This humble bacterium is one of our commensal organisms; it hangs out in our gut being, usually, useful to us. But the reason why every molecular biologists knows about this critter is that it is also the bedrock of DNA manipulation. Molecular biologists shuttle DNA from all sorts of different organisms through E. coli constantly. It is the assembly line for much of molecular biology – where you capture, grow up, extract DNA. The smell of the growth media to grow E. coli infuses all molecular biology labs. E. coli has its own parasites – phages – which are viruses that infect E.coli, and these are as useful as their bacterial host.