Main Question or Discussion Point
Is it fair to say that one-celled organisms who multiply by splitting themselves into two identical entities are, for all practical intent and purposes, immortal?
Sure- and as another example, I have immortalized cell lines from a mouse. There are organisms that can revert back and forth between an 'adult' and 'embryonic' state.Is it fair to say that one-celled organisms who multiply by splitting themselves into two identical entities are, for all practical intent and purposes, immortal?
That would depend on environmental conditions and cells. In the laboratory you can grow cells under identical conditions, so there won't be rapid genetic changes that take over in the population. When the cells experience different conditions, the changes can be quick. I wouldn't be too sure that passage 10 is identical to passage 60.Is that strictly true? I thought clonal cell lines have, for all practical purposes, identical genomes. I'm sure there's mutations and drift, but I thought that's slow enough to allow me to say that cells from (say) passage #60 are the same as passage #10.
With cell lines, it is possible to go back to the same cancer again and again, and have an endless supply of cells. Genetic drift and phenotypic change will be minimal within a laboratory, provided that the cells are not grown continuously — instead, the cells should be replenished from frozen stocks every few weeks — and standard quality control measures are used.
A chromosomal analysis has shown that "the HeLa genome has been remarkably stable after years of continuous cultivation". However, it is also relatively easy to select strains of HeLa that have particular properties by applying selection pressures — deliberately or accidentally — simply by altering the culture conditions, such as the medium or serum. For example, it is possible to select HeLa cells that grow in suspension rather than attached to the culture dish, or HeLa cells that are resistant to cancer drugs.
Mmmm...OK, I understand that, quite often, "common sense" draws more towards what is *common* than to what is *sense*. In lieu of this, I am willing to subject myself to various forms of "tutoring" by people who know either *more* or *different* things (or both!) than myself. Returning to my opening question, which is about a perceived sort of "immortality" in singular celled organisms, I must confess that my agenda is really a different one, and one which is concerned with an almost metaphysical quality of "will" towards complex systems of "local negative entropy" (life) that I seem to intuitively observe as a quality in matter itself; and my hypothesis is that this is a hitherto undescribed force of nature, which works over very large time spans, and subjected to the existing conditions.