Chapter 12 Biology. Cell Division Allows unicellular organisms to reproduce Growth and Repair of multicellular organisms.

Chapter 12

Biology

Cell Division

Allows unicellular organisms to reproduce

Growth and Repair of multicellular organisms.

How Prokaryotic Cells Divide

Prokaryotic cells lack a nucleus and other membranous organelles.

Divide by Binary Fission

Chromosome Is Singular

Prokaryotic chromosome contains mostly DNA and some associated proteins

Asexual reproduction requires a single parent; offspring are genetically identical to parent.

Eukaryotic Chromosomes and the Cell Cycle

• Karyokinesis – nuclear division

• Cytokinesis – division of the cytoplasm

A. Chromosomes

• Histone proteins organize chromosomes.

• Each species has a characteristic number of chromosomes.

A. Chromosomes

• a. Diploid (2n) number includes two sets of chromosomes of each type.

• b. Haploid (n) number contains one of each kind of chromosome.

A. Chromosomes

• Sister chromatids are two parts of a chromosome

• Centromere---a region of constriction on a chromosome

Mitosis

• Centrosomes

– responsible for organizing the spindle.

– main microtubule organizing center of the cell

Mitosis

• The centrosome has divided before mitosis begins.

• Each centrosome contains a pair of barrel-shaped organelles called centrioles; plant cells lack centrioles.

Mitosis Diagram

B. How Animal Cells Divide

• 1. Mitosis:– Interphase

– Prophase

– Pro-metaphase

– Metaphase

– Anaphase

– Telophase.

Mitosis Movie

B. How Animal Cells Divide

Prophase

• a. Chromatin condenses and chromosomes become visible.

• b. Nucleolus disappears and the nuclear envelope fragments.

• c. Short microtubules radiate out from the pair of centrioles located in each centrosome; form starlike asters.

B. How Animal Cells Divide

Prometaphase

• a. attachment of chromosomes to the spindle and movement as they align at the metaphase plate (equator).

B. How Animal Cells Divide

Metaphase

• a. Chromosomes align at the metaphase plate.

B. How Animal Cells Divide

Anaphase

• a. Two sister chromatids of each duplicated chromosome separate at centromere.

• b. Daughter chromosomes, each with a centromere and single chromatid, move to opposite poles.

B. How Animal Cells Divide

Telophase

• a. Spindle disappears.

• b. Chromosomes decondense and return to chromatin; the nuclear envelope reforms and nucleoli reappear.

• c. Cytokinesis is nearly complete.

Cytokinesis in Animal Cells

• a. Cleavage furrow indents the plasma membrane between the two daughter nuclei at a midpoint; progressively divides cytoplasm during cell division.

Mitosis Video

C. How Plant Cells Divide

• 1. Plant meristematic tissue in tips of roots and shoots

• 2. Stages are same as in animal cells.

• 3. Plant cells - no centrioles, and asters do not form.

Cytokinesis in Plant Cells

• Golgi apparatus produces vesicles that move to the midpoint between the daughter cell nuclei

• Vesicles fuse, forming a cell plate

How the Cycle is Controlled

• 1. Some cells divide continuously

• 2. Other cells are arrested in at different stages

Mitosis Stages

How the Cycle is Controlled

• 4. Enzymes known as cyclin-dependent kinases (Cdks) regulate passage of cells through these checkpoints

How the Cycle is Controlled

• Oncogenes (cancer-causing genes) may code for cyclins that no longer function as they should.

Cancer Cells

Cancer Radiation

Cancer Histroy

Cancer Causes

Cancer

• Angiogenesis the formation of new blood vessels.

• Malignancy and Metastasis ability to move and movment of cancer cells to a new location.

Cancer Treatment

Cancer Genetics

The End.

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