stolyar wrote:
It was once believed that cells grown in laboratory tissue cultures were
essentially immortal. That is, as long as all of their needs were met, they
would continue dividing forever. However, it has been shown that normal cells have a finite reproductive limit. A human liver cell, for example,
divides 60 times and then stops. If such a cell divides 30 times and then is
put into a deep freeze for months or even years, it ┬лremembers┬╗ where it
stopped dividing. After thawing, it divides another 30 timesтАФbut no more.
If the information above is accurate, a liver cell in which more than 60
divisions took place in a tissue culture CANNOT be which one of the
following?
(A) an abnormal human liver cell
(B) a normal human liver cell that had been frozen after its first division
and afterward thawed
(C) a normal cell that came from the liver of an individual of a nonhuman
species and had never been frozen
(D) a normal liver cell that came from an individual of a nonhuman
species and had been frozen after its first division and afterward thawed
(E) an abnormal cell from the liver of an individual of a nonhuman species
B ...its would still remember that 59 divisions are left.