The Cell Cycle by: Ernsting at C:\Documents and Settings\Administrator\Local Settings\Temporary Internet Files\Content.IE5\1TIPHCP8\cc03a[1].ppt

Cell division functions in reproduction, growth, and repair

Important Terms (part one) genome: all of a cell’s DNA chromosome: individual DNA molecule chromatin: chromosomal DNA and its protein scaffold sister chromatids: the two identical copies of a duplicated chromosome centromere: the point of attachment for two sister chromatids somatic cells: (most cells) have two copies of each chromosome (diploid) gametes: (reproductive cells; sperm and eggs) have one copy of each chromosome (haploid)

More Important Terms cell cycle: the process of cell division mitosis (M phase) nuclear division interphase: the main part of the cell cycle G1 phase - cell prepares for DNA synthesis, usually grows in size S phase - DNA is duplicated G2 phase - cell checks fidelity of DNA replication, prepares for nuclear division mitosis subphases - prophase, prometaphase, metaphase, anaphase, telophase cytokinesis

Mitosis (1)

Mitosis (2)

The Mitotic Spindle The mitotic spindle is composed of microtubules, and directs the alignment of chromosomes on the metaphase plate. During anaphase, the microtubules attached to each centromere guide the movement of chromosomes toward spindle poles.

Polar Depolymerization of Microtubules

Cytoplasmic Division Microfilaments contract to divide the cytoplasm. Plant cells are less flexible, because of the cell wall, and deposit cell wall material between the two daughter cells.

Mitosis (differential staining)

Mitosis in Growing Tissue

Binary Fission in Bacteria

Evolution of Mitosis

Cell Cycle Control The cell’s place in the cell cycle is signaled by the presence or absence of cell cycle kinases. A growth signal leads to passage through the G0 restriction point into G1. (See Fig 11.11) The cell then executes a programmed series of steps that culminate in mitosis and cytokinesis.

is an example of kinase control of the cell cycle is an example of kinase control of the cell cycle. It is like a license that allows the cell to begin M phase of the cell cycle. MPF MPF is a two-subunit enzyme. One subunit is Cdk (present during the whole cell cycle). The other subunit is a cyclin protein that builds up as M phase approaches. When the cyclin concentration is high enough, cyclin binds to Cdk, forming the MPF enzyme. MPF activity signals the start of mitosis.

Cancer Normal cells are transformed to tumor cells when cell division is not controlled. Cancer cells are growth-factor independent. Cancer cells have escaped density-dependent inhibition. Most cancerous cells are destroyed by the immune system, but some cells progress from benign to malignant, and possibly to metastatic.

Cell Culture and Growth Factors

Density-dependent Inhibition Density-dependent inhibition is a property of normal cells. Cancer cells lack this inhibition.

Metastatic Cancer Metastatic cancer cells spread throughout the body.