Search results
Results from the WOW.Com Content Network
In the budding yeast S. cerevisiae, Clb1 is the main meiotic regulatory cyclin, though Clb3 and Clb4 are also expressed during meiosis and activate a p34 cdc28-associated kinase immediately prior to the first meiotic division. [73] The IME1 transcription factor drives entry into meiotic S-phase and is regulated according to inputs like nutrition.
S phase (Synthesis phase) is the phase of the cell cycle in which DNA is replicated, occurring between G 1 phase and G 2 phase. [1] Since accurate duplication of the genome is critical to successful cell division, the processes that occur during S-phase are tightly regulated and widely conserved.
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
In S phase, the chromosomes are replicated in order for the genetic content to be maintained. [18] During G 2, the cell undergoes the final stages of growth before it enters the M phase, where spindles are synthesized. The M phase can be either mitosis or meiosis depending on the type of cell.
BRCA1 is known to be required for S and G2/M transitions, and is involved in the cellular response to DNA damage. BRCA2 is believed to be involved in homologous recombination and regulating the S-phase checkpoint, and mutations of deficiencies in BRCA2 are strongly linked to tumorigenesis. [36]
In general, cohesion is established during S phase as DNA is replicated, and is lost when chromosomes segregate during mitosis and meiosis. Some studies have suggested that cohesion aids in aligning the kinetochores during mitosis by forcing the kinetochores to face opposite cell poles. [1]
The red horizontal line represents time in S-phase, from early (top) to late (bottom). Grey data points each represent a different DNA sequence position along the length of chromosome 2 as indicated on the x axis, with more positive values on the y-axis indicating earlier replication.
During the phase of meiosis labeled “interphase s” in the meiosis diagram there is a round of DNA replication, so that each of the chromosomes initially present is now composed of two copies called chromatids. These chromosomes (paired chromatids) then pair with the homologous chromosome (also paired chromatids) present in the same nucleus ...