Mean generation time

The time interval between one cell division and the next is called the generation time. When considering a growing culture containing many thousands of cells, a mean generation time is usually calculated. 

If this time interval is t, then the mean generation time G is given by the expression ... 

The mean generation time of a red cell, from the stem cell to a mature reticulocyte, is 90 h. The phase in the cell generation pathway in which most of the hemoglobin is synthesized is 40h. How many hemoglobin molecules are synthesized per human red blood cell per second ... 

It is convenient to define a mean generation time, t2, which is the time it takes for the number of cells to double during the exponential phase. This is the time corresponding to In n/n, = In 2 so that from (10.82 ... 

If an individual cel is observed it will be seen to increase in size and eventually divide into, two daughter cells, each of which will grow and later divide. The time between one cell division and the next is the generation time, and varies very widely for a given type of cell. The mean generation time is the mean time for all the cells in a given culture, under the particular conditions of the experiment. 

In the example just considered there was no lag phase, and could therefore be taken to be the number of cells at the beginning of the experiment. If there is a lag phase, the mean generation time must be calculated from data taken within the exponential phase, and the duration of the lag phase can then be calculated. The procedure is best illustrated by an example. 

A culture medium was inoculated with 5.0 x 10 cells of Aerobacter aerogenes. After 100 minutes the system had entered the exponential phase and there were 1.2 x 10 cells. After 300 minutes it was still in the exponential phase and there were 3.5 x 10 cells. Calculate the specific growth rate, the mean generation time within the exponential phase, and the duration of the lag phase. 

After 5 hours there were found to be 1.5 x 10" cells, and a lag period of 90 minutes was observed. Calculate the specific growth rate and the mean generation time during the exponential phase. 

In order to obtain numerical predictions from (7.11), we need values for the parameters appropriate to the Neolithic transition. As explained in Sect. 7.1.1, such values have been obtained from independent observations of the Neolithic expansion and their mean values are rj = 0.032 yr , D = 15.44 km /yr, and tj = T/2 = 12.5 yr. The latter value follows from the mean generation time T = 25 yr. On... 

Fastest mean generation time during autotrophic... 

Hux averaged "inverse velocity" Flux averaged cross section = "mean generation time"... 

Delayed neutron generation time, r, is the weighted average of the mean generation times of the six delayed neutron precursors. Table 3.7 is a compilation of delayed neutron data for uranium 235 from Table 3.4. 

Table 3.7 Uranium 235 Delayed Neutron Mean Generation Time...

Precursor Group Decay Constant Xi (sec ) Mean Generation Time ri-i/Xi (sec ) Precursor Fraction, Pi Weighted Generation Time, TiPi (sec)... 

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