Mitosis • Mitosis is the process by which new cells are generated. • Mitosis produces 2 genetically identical daughter cells
Overview of Mitosis: Parent cell Replicated chromosomescondense at the start of mitosis Mitosis Sister chromatids separate and two daughter cells are formed. Parent cell and daughter cell contain thesame complement of chromosomes.
Figure 12.5 The stages of mitotic cell division in an animal cell: G2 phase; prophase; prometaphase
Figure 12.5 The stages of mitotic cell division in an animal cell: metaphase; anaphase; telophase and cytokinesis.
The kinetochore is a specialized region on the centromere where spindle fibers attach
Motor molecules of the kintochore walk along the microtubule, taking the chromosome with it As the chromosomes move toward the poles, the microtubules are broken down at the kinetochore end
ATP ADP+Pi Motor molecules "walk" along a microtubule track Transport vesicle ATP ADP+Pi Kinesin Microtubule
After the nucleus divides, cytokinesis divides the cytoplasm, forming two separate cells
Figure 8.9a Cytokinesis in animals Cleavage furrow
Unregulated cell division can lead to cancer • Many factors interact with each other to determine whether a cell will undergo mitosis • Cell cycle checkpoints normally insure that DNA replication and mitosis occur only when conditions are favorable and the process is working correctly.
Cell-Cycle Checkpoints G2 checkpoint Pass this checkpoint if:• cell size is adequate• chromosome replication is successfully completed M Mitosis G2 Second gap Metaphase checkpoint Pass this checkpoint if:• all chromosomes are attached to mitotic spindle G1 First gap G1 checkpoint DNA synthesis Pass this checkpoint if:• cell size is adequate• nutrient availability is sufficient• growth factors (signals from other cells) are present S
Cell cycle proteins regulate whether a cell will proceed past a particular cell cycle checkpoint • cyclin- a protein whose amount varies cyclically • cdk- another cell division control protein - a cyclin dependent kinase; active only when bound to cyclin • MPF- mitotic promoting factor... • MPF is a kinaseenzyme, ones that switches on/off target proteins by phosphorylating them..... • [cyclin + cdk = MPF]... favors Mitosis • leads to destruction of cyclin itself
Growth factor proteins are signal molecules that trigger a signal-transduction pathway leading to cell division Platelet-derived growth factor
Unregulated cell division can lead to cancer • Mutations in genes that encode cell cycle proteins can lead to unregulated growth, resulting in tumor formation and ultimately invasion of cancerous cells to other organs.