25-09-07: stopping the evolution

"To renew themselves, epithelial tissues retain a population of undifferentiated stem cells, like the unformed cells present in embryos, that have the ability to grow into different types of cells. When replacements are needed, some of these stem cells divide to make transient amplifying cells (TACs). The TACs then divide several times, and Pepper and his co-workers think that each division produces cells that are a little more developed into mature tissue cells.All this costs a lot of metabolic energy, so it is not very efficient.
But, the researchers say, it means that the functions of self-replication and proliferation are divided between separate groups of cells. The stem cells replicate, but only a little, and so there's not much chance for mutations to arise or for selective pressure to fix them in place. The proliferating TACS may mutate, but they aren't simply copying themselves, so there isn't any direct competition between the cells to create an evolutionary pressure. As a result, evolution can't get started.Pepper and his colleagues have used computer modelling to show that this proposed mechanism can suppress evolution in a long-lived, multicelled organism."

copied from the nature news Why a person doesn't evolve in one lifetime, it is another notice to me that how many things that ignored by me (and maybe many others) are in fact so essential. What a simple question, but never being alarmed to me. Just remind self - you are so lack of attention and knowledge.

Back to work, electron microscopy is a tricky thing, I guess I have to practise for a long time to be familiar with it. However, it is interesting.

I have to admit, that novels are much better for lesiure time, compare to the literatures. I finished reading of Harry Potter series in one month, I learnt loads of new word from it, it is definitely an enhancement to my English vocabulary. I am now picking up another series named "Horus Heresy", which belongs to the Warhammer 40,000 world. I will get to some serious reading soon - don't forget that I still have the Sir Furgeson and Nietzsche's books waiting.