A dark kinase
Spermatozoa. There are no other cells in humans - or indeed in any other animals - that have the capacity to wriggle and move forward the way spermatozoa do. Blood cells may dash around our bodies but they can only do so because they are swept up in the pulse and flow of blood. Spermatozoa make progress like little animals - which is why they were called 'animalcules' by the Dutch microbiologist van Leeuwenhoek who was the first to observe them under a microscope in the 17th century. Many organisms can move like spermatozoa, such as bacteria or protists for example, but these are unicellular from the start and really only have themselves to depend upon. Spermatozoa cannot survive on their own, as they don't have the genetic makeup for that, but they can move on their own. In fact, locomotion is really all they have evolved for. Their sole aim is to reach an ovum into which they will inject their DNA. So evolution has trimmed the architecture of spermatozoa down to the very essential: a head (in which resides the nucleus) attached to a powerful tail. The tail itself is a model of biological design and technology brought about by many proteins, among which a crucial kinase known as STK33.
