<P> In the rod - shaped bacteria E. coli, Caulobacter crescentus and B. subtilis cell size is controlled by a simple mechanisms in which cell division occurs after a constant volume has been added since the previous division . By always growing by the same amount, cells born smaller or larger than average naturally converge to an average size equivalent to the amount added during each generation . </P> <P> Cell reproduction is asexual . For most of the constituents of the cell, growth is a steady, continuous process, interrupted only briefly at M phase when the nucleus and then the cell divide in two . </P> <P> The process of cell division, called cell cycle, has four major parts called phases . The first part, called G phase is marked by synthesis of various enzymes that are required for DNA replication . The second part of the cell cycle is the S phase, where DNA replication produces two identical sets of chromosomes . The third part is the G phase in which a significant protein synthesis occurs, mainly involving the production of microtubules that are required during the process of division, called mitosis . The fourth phase, M phase, consists of nuclear division (karyokinesis) and cytoplasmic division (cytokinesis), accompanied by the formation of a new cell membrane . This is the physical division of "mother" and "daughter" cells . The M phase has been broken down into several distinct phases, sequentially known as prophase, prometaphase, metaphase, anaphase and telophase leading to cytokinesis . </P> <P> Cell division is more complex in eukaryotes than in other organisms . Prokaryotic cells such as bacterial cells reproduce by binary fission, a process that includes DNA replication, chromosome segregation, and cytokinesis . Eukaryotic cell division either involves mitosis or a more complex process called meiosis . Mitosis and meiosis are sometimes called the two "nuclear division" processes . Binary fission is similar to eukaryote cell reproduction that involves mitosis . Both lead to the production of two daughter cells with the same number of chromosomes as the parental cell . Meiosis is used for a special cell reproduction process of diploid organisms . It produces four special daughter cells (gametes) which have half the normal cellular amount of DNA . A male and a female gamete can then combine to produce a zygote, a cell which again has the normal amount of chromosomes . </P>

When would the quantity of dna double when growing cells