frankandmel at email.msn.com
Tue Apr 11 01:45:30 EST 2000
I think I may be able to help a little, since I have also had problems
with passage numbers. As far as I know, if one were to split the cells at
exactly the right moment from one perfect container to another, and these
cells never reverted to different phenotypes/genotypes, then the passage
number would be meaningless.
Unfortunately, This is almost never the case. Because of this, every time
one splits the cells, one phenotype out of the multitude of slightly
differing cells is chosen as the optimal one for the new growth conditions.
Cells with this phenotype will grow better/faster, changing the average
phenotype of the entire colony slightly. Additional passages will change
the cells further.
The passage number is used to signal how many selection events (passages)
that have occurred since one knew what the phenotype of the cells was. A
cell line that has been passaged ten times is likely to be closer to one
that has been passaged 200 times, even if the total number of cells produced
is the same.
It is also worth noting that cells that have only been passaged 2-4 times
since being frozen may act strangely for a while as a side effect of the
Another problem with passage numbers that I had was that one cell line I was
using died after 30 passages. Every time the cells hit the 30 passage mark,
they could get sickly and die within 2-3 additional passages. We never
found out what was causing this, and were instead forced to low passage
Hope this helped,
Frank Beissel IV
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