Elliott, McLaughlin, 1978 PNAS rate of macromolecular synthesis through cell cycle of the budding yeast

 

Elliott, McLaughlin, 1978 PNAS rate of macromolecular synthesis through cell cycle of the budding yeast

DNA synthesis is periodic. Rate of RNA and protein synthesis is an exponential increase.  

Based on bulk measurement by isotope labeling. 

The rate of RNA synthesis divided by total RNA is constant (Figure 3C), and the rate of protein synthesis divided by total protein is also constant (Figure 3A). So, the apparent rate of RNA/protein increase exponentially during cell cycle. 

         dM / M = C dt  which means d(log(M) = C dt, so, M = exp( C t). 

 

Talia, Cross, 2007, The effects of molecular noise and size control on variability in the budding yeast cell cycle

The effects of molecular noise and size control on variability in the budding yeast cell cycle

Talia, ... Cross, Nature, 2007, 

"The variability in G1 decreases with the square root of the ploidy through a 1N/2N/4N ploidy series, consistent with simple stochastic models for molecular noise."

Cell size control contributes significantly to G1 variability in daughter cells but not in mother cells. However, even in daughters, size-independent noise is the largest quantitative contributor to G1 variability.

Exit of the transcriptional repressor Whi5 from the nucleus partitions G1 into two temporally uncorrelated and functionally distinct steps. The first step, which depends on the G1 cyclin gene CLN3, corresponds to noisy size control that extends G1 in small daughters, but is of negligible duration in mothers. The second step, whose variability decreases with increasing CLN2 gene dosage, is similar in mothers and daughters. This analysis decomposes the regulatory dynamics of the Start transition into two independent modules, a size sensing module and a timing module, each of which is predominantly controlled by a different G1 cyclin.

Start: what does it mean? It seems to be a made-up term for something we do not actually understand. 

Cooper 2006, BMC, Distinguishing between linear and exponential cell growth during the division cycle: Single-cell studies, cell-culture studies, and the object of cell-cycle research

 

Cooper, 2006.  Distinguishing between linear and exponential cell growth during the division cycle: Single-cell studies, cell-culture studies, and the object of cell-cycle research

This is a commentary. Cooper seems to be a biologist, argues that mass measurement is more accurate on single cell study to understand growth 'law'. This seems to be contrary to the statistical physics argument. The commentary is mostly philosophical and are based on the best-fit argument of experimental data. 

Cooper main argument that exponential growth is the universal growth law also assumes abundant resources. Cooper said that linear growth is due to experimental measurement limitation also did not take ecological constraints and biological competition into account. 

Cooper cited Michison's linear growth model based on 4 decades of works.