this phase is usually the most variable with respect to time, and is typically longest cells that do not divide become arrested in this phase, then called G0 the period between the S phase and cell division is the G2 phase the G2 is usually short; cells in this phase are committed to and preparing for cell division cell division has two main parts mitosis and cytokinesis – mitosis is the process that distributes a complete copy of the duplicated genetic information to each daughter cell cytokinesis is the process of dividing the cytoplasm into two separate cells some cells can have mitosis without cytokinesis (most common in fungi and slime molds) the current model of cell cycle regulation involves a highly conserved, genetically-controlled program that can be influenced by external signals there are three major checkpoints, found in G1, G2 and mitosis key regulatory components for checkpoints are cyclins and cyclin-dependent protein kinases hormones such as cytokinins in plants and various protein growth factors in animals can stimulate progression through checkpoints in the right cells under the right conditions other factors can serve as suppressors of cell division cancer cells generally grow without needing stimulation by external growth factors and fail to respond to normal suppressors of cell division is generally be divided into 4 stages: and (PMAT) mitosis prophase, metaphase, anaphase, telophase be aware that mitosis is a continuous process, the stages are defined only for our convenience prophase chromatin condenses to form chromosomes – each chromosome (duplicated during S phase) forms a pair of sister chromatids sister chromatids are joined at a centromere by protein tethers centromeres contain a kinetochore where microtubules will bind each sister chromatid has its own kinetochore a system of microtubules, called the mitotic spindle, organizes between the two poles (opposite ends) of the cell each pole has a microtubule organizing center (MTOC) in animals and some other eukaryotes, centrioles are found in the MTOC by the end of prophase: the nuclear membrane has disappeared (actually divided into many small vesicles) nucleoli have disintegrated
this phase is usually the most variable with respect to time, and is typically longest cells that do not divide become arrested in this phase, then called G0 the period between the S phase and cell division is the G2 phase the G2 is usually short; cells in this phase are committed to and preparing for cell division cell division has two main parts – mitosis and cytokinesis mitosis is the process that distributes a complete copy of the duplicated genetic information to each daughter cell cytokinesis is the process of dividing the cytoplasm into two separate cells some cells can have mitosis without cytokinesis (most common in fungi and slime molds) the current model of cell cycle regulation involves a highly conserved, genetically-controlled program that can be influenced by external signals there are three major checkpoints, found in G1, G2 and mitosis key regulatory components for checkpoints are cyclins and cyclin-dependent protein kinases hormones such as cytokinins in plants and various protein growth factors in animals can stimulate progression through checkpoints in the right cells under the right conditions other factors can serve as suppressors of cell division cancer cells generally grow without needing stimulation by external growth factors and fail to respond to normal suppressors of cell division mitosis is generally be divided into 4 stages: prophase, metaphase, anaphase, and telophase (PMAT) be aware that mitosis is a continuous process, the stages are defined only for our convenience prophase – chromatin condenses to form chromosomes each chromosome (duplicated during S phase) forms a pair of sister chromatids sister chromatids are joined at a centromere by protein tethers centromeres contain a kinetochore where microtubules will bind each sister chromatid has its own kinetochore a system of microtubules, called the mitotic spindle, organizes between the two poles (opposite ends) of the cell each pole has a microtubule organizing center (MTOC) in animals and some other eukaryotes, centrioles are found in the MTOC by the end of prophase: the nuclear membrane has disappeared (actually divided into many small vesicles) nucleoli have disintegrated
chapter12activity.docx