BIOL 102 Lecture Notes - Lecture 31: Prophase, Interphase, Metastasis
Document Summary
As mitosis approaches, the microtubules move from their interphase arrangement and form the spindle, which grows until it fills the whole cell. It is the microtubule organizing centre (mtoc) of the cell, like the root of a plant: a pair of centrioles perpendicular to each other generate the microtubules needed for cell motility (cilia, flagella) No centrosomes are present in angiosperms (flowering plants); the spindle forms from microtubules that assemble in all directions from multiple mtocs surrounding the entire nucleus. Kinetochore microtubules connect the chromosomes to the spindle poles, nonkinetochores overlap with opposite ones: chromosomes walk themselves to the poles using motor proteins and kinetochores. Hormones, growth factors, and other external controls control the cell cycle by stimulating or inhibiting division. Cyclin-dependent kinases (cdk) are protein kinases that add phosphate groups to target proteins when they are combined with a cyclin protein. Cyclin concentration fluctuates during the cell cycle so cdk activity does too.
