Mader: Biology 8 th Ed. The Cell Cycle and Cellular Reproduction Chapter 9

Mader: Biology 8 th Ed. Outline Interphase Mitotic Stage Cell Cycle Control Apoptosis Mitosis Mitosis in Animal Cells Cytokinesis Cancer Prokaryotic Cell Division

Mader: Biology 8 th Ed. Interphase Most of the cell cycle is spent in interphase. – G 1 - Cell doubles its organelles and accumulates materials needed for DNA synthesis. – S - DNA replication. – G 2 - Cell synthesizes proteins necessary for cell division.

Mader: Biology 8 th Ed. Mitotic Stage Cell division stage that includes mitosis (nuclear division) and cytokinesis (cytoplasm division).

Mader: Biology 8 th Ed. Cell Cycle

Mader: Biology 8 th Ed. Cell Cycle Control Researchers have identified internal signal protein (cyclin) that increases and decreases as cell cycle continues. – Must be present for the cell to proceed from the G 2 stage to the M stage and from G 1 stage to S stage.  Allows time for any damage to be repaired.

Mader: Biology 8 th Ed. Cell Cycle Control

Mader: Biology 8 th Ed. Apoptosis Often defined as programmed cell death. – Cells routinely harbor enzymes (caspases) necessary for apoptosis to occur.  Ordinarily held in check by inhibitors, but can be unleashed by internal or external signals. Mitosis increases and apoptosis decreases the number of somatic cells.

Mader: Biology 8 th Ed. Apoptosis

Mader: Biology 8 th Ed. Mitosis When a eukaryotic cell is not undergoing division, the DNA within the nucleus is a tangled mass of chromatin. – Condenses into chromosomes  Each species has a characteristic number of chromosomes.  Diploid (2n) - Two of each kind.  Haploid (1n) - One of each kind.

Mader: Biology 8 th Ed. Mitosis During mitosis, a diploid nucleus divides to produce diploid daughter nuclei. – Two identical chromatids are called sister chromatids.  Attached to each other at centromere.  During nuclear division, sister chromatids separate at the centromeres, and each duplicated chromosome gives rise to two daughter chromosomes.

Mader: Biology 8 th Ed. Duplicated Chromosomes

Mader: Biology 8 th Ed. Mitosis in Animal Cells Each centromere in an animal cell contains a pair of barrel-shaped organelles (centrioles) and an array of short microtubules (aster). – Centromeres organize mitotic spindle, which contains many fibers, each composed of a microtubule bundle.

Mader: Biology 8 th Ed. Mitosis in Animal Cells Prophase – Chromatin has condensed. – Nucleolus disappears. – Nuclear envelope disintegrates. – Spindle begins to assemble. Prometaphase – Kinetochores develop on centromere.  Attach sister chromatids to spindle fibers.

Mader: Biology 8 th Ed.

Mitosis in Animal Cells Metaphase – Chromosomes, attached to kinetochore fibers, are in alignment at center of cell. Anaphase – Sister chromatids split, producing daughter chromosomes.  Daughter chromosomes are pulled to opposite poles.

Mader: Biology 8 th Ed. Mitosis in Animal Cells Telophase – Spindle disappears as new nuclear envelopes form around the daughter chromosomes.  Chromosomes become diffuse chromatin again.  Nucleolus appears in each daughter nucleus.

Mader: Biology 8 th Ed.

Plant Cell Division Meristematic plant tissue retains the ability to divide throughout the plant’s life. – Found at root and shoot tips.

Mader: Biology 8 th Ed. Phases of Mitosis in Plant Cells

Mader: Biology 8 th Ed. Cytokinesis Cytokinesis accompanies mitosis in most cells, but not all. – Mitosis without cytokinesis results in a multinucleated cell.  Begins in anaphase, continues in telophase, but does not reach completion until the following interphase begins.

Mader: Biology 8 th Ed. Cytokinesis Animal Cells – Cleavage furrow, membrane indentation between daughter nuclei, begins as anaphase nears completion.  Deepens when a band of actin filaments (contractile ring) forms a circular constriction between the two daughter cells.

Mader: Biology 8 th Ed. Cytokinesis in Animal Cells

Mader: Biology 8 th Ed. Cytokinesis Plant Cells – Rigid cell wall surrounding plant cells does not permit cytokinesis by furrowing.  Begins with formation of a cell plate which eventually becomes new plasma membrane between the daughter cells.

Mader: Biology 8 th Ed. Cytokinesis in Plant Cells

Mader: Biology 8 th Ed. The Cell Cycle and Cancer Cancer is a growth disorder that results from the mutation of genes regulating the cell cycle. – Carcinogenesis, development of cancer, tends to be gradual.

Mader: Biology 8 th Ed. Characteristics of Cancer Cells Lack differentiation. Have abnormal nuclei. Form tumors. – Loss of contact inhibition. Undergo metastasis. – New tumors distant from primary tumor. Undergo angiogenesis. – Formation of new blood vessels.

Mader: Biology 8 th Ed.

Origin of Cancer Mutations in DNA repair mechanisms. Mutations to proto-oncogenes and tumor- suppressor genes. – Proto-oncogenes become oncogenes. Telomerase allows cancer cells to continually divide.

Mader: Biology 8 th Ed. Prokaryotic Cell Division Asexual Reproduction - offspring are genetically identical to the parent. – Binary fission produces two (binary) daughter cells that are identical to the original parent.  Prokaryotes contain a single chromosome with only a few proteins.

Mader: Biology 8 th Ed. Binary Fission

Mader: Biology 8 th Ed. Review Interphase Mitotic Stage Cell Cycle Control Apoptosis Mitosis Mitosis in Animal Cells Cytokinesis Cancer Prokaryotic Cell Division

Mader: Biology 8 th Ed.