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. Author manuscript; available in PMC: 2019 Apr 1.
Published in final edited form as: Curr Opin Syst Biol. 2018 Feb 2;8:109–116. doi: 10.1016/j.coisb.2018.01.002

Figure 3. Potential mechanisms driving gene-product concentration homeostasis demonstrated at the RNA level.

Figure 3

a) The rate of transcription (number of mRNAs synthesizes per unit time) of an individual gene increases proportionally with size in single cells, with a size-invariant decay rate. Both haploid (light violet) and diploid (vilot) cells exhibit similar scaling due to gene dosage compensation. b) The transcription rate is independent of gene dosage and cell size, and the mRNA stability (decay rate) decreases with cell size to maintain a fixed concentration. c) The rate of transcription is size-independent and increases by approximately 2-fold upon gene replication. A strong coupling between cell size and gene dosage leads to concentration homeostasis. Unlike the first two strategies, here homeostasis is not perfect as mRNA concentrations will decrease with increasing size for fixed ploidy.