10-2 The Cell Cycle Cell Growth

I. Prokaryote/bacteria Cell Division A. Binary Fission - Division in prokaryote and bacteria cells. An asexual division that reproduces identical products. B. Animal and plant cells do not reproduce in this way, they reproduce through mitosis.

II. Cell Division’s A. Mitosis: body cell division resulting in two cells with identical genetic material 1. 46 chromosomes to 46 B. Meiosis: reproductive cells reducing the number of chromosomes by half from 46 to 23 chromosomes. 1. Also called Reduction Division.

III. The Cell Cycle A. The repeating set of events that make up the life of a cell. 1. Interphase- The longest stage of the cell cycle, G1, S, G2 phases 2. M phase: the dividing phase, prophase, metaphase, anaphase, telophase. 3. Cytokinesis: division of cytoplasm of a cell

IV. Interphase: Non-dividing phase A. G1 phase: offspring cells grow to mature size B. S phase: cell’s DNA is copied C. G2 phase: cell prepares for division D. G0 phase: cells that do not divide after maturity. Heart muscle, brain and nerve cells.

Early Interphase

The M- Phase

1. DNA tightens into rod-shaped chromosomes. A. Prophase 1. DNA tightens into rod-shaped chromosomes. 2. Centromere connects the two sister chromatids 3. Nucleolus and nuclear membrane disappears

4. Centrosomes- dark material that appears next to the disappearing nucleus, containing a pair of cylinder shaped bodies called centrioles, (animals cells only) 5 Spindle fibers radiate from the centromeres and form the mitotic spindle. This equally divides the chromatids.

F. 2 kinds of Spindle Fibers 1. Kinetochore fibers attach to a protein called kinetochore found in the centromere region, and move the chromosomes 2. Polar fibers extend across the dividing cell from one centrosome to the other centrosome.

Prophase

2. Metaphase A. Kinetochore fibers move the chromosomes to the center of the dividing cell 1). Chromosomes are easily seen lined up in the middle of the cell

Metaphase

3. Anaphase A. Sister chromatids separate at the centromere and move toward opposite ends of the cell 1). They are pulled centromere first, making it look like they are being dragged.

Early Anaphase

Late Anaphase

4. Telophase A. Chromosomes are now at opposite ends 1). Spindle fibers disassemble. 2). Chromosomes relax and turn into chromatin. 3). Nuclear envelope and nucleolus reforms.

Telophase

5. Cytokinesis A. Dividing of the cytoplasm 1). Cleavage furrow forms between the two poles of an animal cell. 2). This pinches the cell into two. 3). In plants, a cell plate or wall forms from vesicles, separating the two halves.