the mass of dna increases in the cell cycle at the beginning of dna replication.
when does the mass of dna increase in the cell cycle?
beginning of dna replication
the cell cycle, or cell-division cycle, is the series of events that take place in a cell leading to duplication of its dna (dna replication) and division of cytoplasm and organelles to produce two daughter cells. in bacteria, which lack a cell nucleus, the cell cycle is divided into the b, c, and d periods. the b period extends from the end of cell division to the beginning of dna replication. dna replication occurs during the c period. the d period refers to the stage between the end of dna replication and the splitting of the bacterial cell into two daughter cells. in cells with a nucleus, as in eukaryotes, the cell cycle is also divided into two main stages: interphase and the mitotic (m) phase (including mitosis and cytokinesis). during interphase, the cell grows, accumulating nutrients needed for mitosis, and undergoes dna replication preparing it for cell division. during the mitotic phase, the replicated chromosomes and cytoplasm separate into two new daughter cells. to ensure the proper division of the cell, there are control mechanisms known as cell cycle checkpoints.
cell cycle
multiparameter analysis of the cell cycle includes, in addition to measurement of cellular dna content, other cell cycle related constituents/features. the concurrent measurement of cellular dna and rna content, or dna susceptibility to denaturation at low ph using the metachromatic dye acridine orange, reveals the g, g, and g cell cycle compartments and also makes it possible to discriminate between s, g and mitotic cells. the cells in g are quiescent, temporarily withdrawn from the cell cycle (also identifiable as g), the g are in the growth phase while g are the cells just prior entering s, with their growth (rna and protein content, size) similar to that of the cells initiating dna replication. similar cell cycle compartments are also recognized by multiparameter analysis that includes measurement of expression of cyclin d1, cyclin e, cyclin a and cyclin b1, each in relation to dna content concurrent measurement of dna content and of incorporation of dna precursor 5-bromo-2'-deoxyuridine (brdu) by flow cytometry is an especially useful assay, that has been widely used in analysis of the cell cycle in vitro and in vivo. however, the incorporation of 5-ethynyl-2'-deoxyuridine (edu), the precursor whose detection offers certain advantages over brdu, has now become the preferred methodology do detect dna replicating (s-phase) cells.
cell cycle analysis