University:
Harrisburg University of Science and Technology
Course:
BIOL 281 | Cell Biology Lecture
Academic year:

2021
Views:

436

Pages:

1
Author:

Clint W.

Cell Division Cell Cycle The cell cycle is an ordered set of events that culminates in cell division M phase A M P C T Interphase An active phase of the cell cycle where many metabolic reactions occur • Consists of G1, S and G2 stages G1 Growth and metabolism G2 S Growth and preparation Replication of DNA Interphase M phase The period of a cell cycle in which the cell and contents divide • Consists of mitosis (P, M, A, T) and cytokinesis Some cells may also enter a non-proliferative quiescent phase (G0) Interphase Supercoiling Normal metabolism cannot occur during M phase, so key events must occur during interphase to prepare for division: During mitosis, chromatin condenses via supercoiling to become tightly packed chromosomes • Due to replication (S phase), chromosomes consist of identical sister chromatids (joined at a centromere) • • • • • • DNA replication (during S phase) Organelle duplication Cell growth Transcription / translation Obtaining nutrients Respiration (cellular) S phase Mitosis Mitosis Cytokinesis Mitosis is the division of a diploid nucleus into two genetically identical diploid nuclei Cytokinesis is the process of cytoplasm division, whereby a cell splits in two • It occurs concurrently with telophase and differs in plants and animals This process of cell cloning is needed for many important processes: Animals: • Microtubules form a concentric ring and contract towards the centre (centripetal) • • • • Tissue repair Organism growth Asexual reproduction Development of embryos Plants: • Vesicles form at the cell centre and fuse outwards to form a cell plate (centrifugal) Mitotic Index Mitosis Micrographs The mitotic index is a measure of the proliferative status of a cell population (i.e. number of dividing cells) The mitotic index will be elevated during growth and repair processes and acts as a prognostic tool for cancer Mitotic Index = Cells in mitosis* Total number of cells *Mitotic cells have no nucleus and have visible chromosomes Prophase Metaphase Anaphase Telophase