Aim: How is the cell cycle regulated? Do Now: 1.Worksheet HW: Study for test tomorrow

The Cell Cycle Most of a cell’s life is spent in a nondividing state (interphase) Body (somatic) cells divide in three stages – DNA replication duplicates genetic material exactly – Mitosis divides genetic material equally – Cytokinesis divides cytoplasm and organelles into two daughter cells Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

A Cell’s Life Cycle Figure 3–23 The Cell Life Cycle.

A Cell’s Life Cycle Interphase – The non-dividing period G-zero (G 0 ) phase—specialized cell functions only G 1 phase—cell growth, organelle duplication, protein synthesis S phase—DNA replication and histone synthesis G 2 phase—finishes protein synthesis and centriole replication Mitosis Duplicated DNA divides into two sets of chromosomes

Regulating the Cell Life Cycle Normally, cell division balances cell loss Increased cell division – Internal factors (M-phase promoting factor, MPF) – Extracellular chemical factors (growth factors) Decreased cell division – Repressor genes (faulty repressors cause cancers) – Worn out telomeres (terminal DNA segments) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Control of Cell Destiny MPF- Maturation promoting factor (MPF) – Signal that induces cell division. – Consists of group of enzymes called cdc2 proteins (and proteins called cyclins. Cyclins build up during interphase and then activates cdc2 proteins which activates MPF which results in cell division. Apoptosis – Programmed cell death

Tumor Suppressor Genes Produce proteins that normally inhibit cell division. – Loss or alternation of p53 gene leads to breast cancer, colon cancer, and other tumors. – Normal p53 gene protein arrests a cell in G1 which prevents cell division. Repair of damaged DNA and induces apoptosis in the cells where repair was not successful

Oncogenes Most oncogenes are mutations of certain normal genes called proto-oncogenes. When a proto-oncogene mutates (changes) into an oncogene, it becomes a "bad" gene that can become permanently turned on or activated when it is not supposed to be.

1 Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol (a) INTERPHASE Centrioles Centrosome: all at 700x LM 1 Late Early Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol Chromosome (two chromatids joined at centromere (a) INTERPHASE (b) PROPHASE Centrioles Centrosome: Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore 2 all at 700x LM Centromere 1 Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol Metaphase plate (a) INTERPHASE Centrioles Centrosome: (c) METAPHASE 2 3 Late Early (b) PROPHASE Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore all at 700x LM Chromosome (two chromatids joined at centromere Centromere 1 Early Late (d) ANAPHASE Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol Chromosome (a) INTERPHASE Centrioles Centrosome: (c) METAPHASE Cleavage furrow Late Early (b) PROPHASE Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore Metaphase plate all at 700x LM Chromosome (two chromatids joined at centromere Centromere 1 Early Late (d) ANAPHASE Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol (a) INTERPHASE Centrioles Centrosome: Cleavage furrow (e) TELOPHASE (c) METAPHASE Cleavage furrow Late Early (b) PROPHASE Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore Metaphase plate Chromosome all at 700x LM Chromosome (two chromatids joined at centromere Centromere 1 Early Late (d) ANAPHASE Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol (a) INTERPHASE Centrioles Centrosome: (f) IDENTICAL CELLS IN INTERPHASE Cleavage furrow (e) TELOPHASE (c) METAPHASE Cleavage furrow Late Early (b) PROPHASE Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore Metaphase plate Chromosome all at 700x LM Centromere Chromosome (two chromatids joined at centromere

– Rate of cell division Slower mitotic rate means longer cell life – Muscle cells, neurons rarely divide – Exposed cells (skin and digestive tract) live only days or hours. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Mitotic Rate

Tumors and Cancer Cancer develops in steps – Abnormal cell – Primary tumor – Metastasis – Secondary tumor Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tumors and Cancer Figure 3–26 The Development of Cancer. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Summary Why is interphase important to a cell? Distinguish mitosis and meiosis. Define apoptosis Why are tumor suppressor genes important?

Regulating the Cell Life Cycle Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings