The Cell Cycle Why Do Cells Divide Reproduce

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The Cell Cycle

The Cell Cycle

Why Do Cells Divide? – Reproduce • single celled organisms – Repair • Replace

Why Do Cells Divide? – Reproduce • single celled organisms – Repair • Replace old cells – Growth • we all start out as a single cell…

Before Division… • DNA must condense. – Loose DNA = Chromatin – Condensed DNA

Before Division… • DNA must condense. – Loose DNA = Chromatin – Condensed DNA = Chromosome • How chromosomes form: – DNA wraps around proteins (histones), this continues to coil until condensed. DNA double helix DNA and histones Chromatin Supercoiled DNA

Chromosome Structure • Chromatid = One half of a duplicated chromosome. • Sister chromatids

Chromosome Structure • Chromatid = One half of a duplicated chromosome. • Sister chromatids are held together at the centromere. chromatid centromere

3 Stages of the Cell Cycle • Interphase • Mitosis • Cytokinesis Did you

3 Stages of the Cell Cycle • Interphase • Mitosis • Cytokinesis Did you know…Cell division may be as fast as 30 minutes (in some bacteria) or never (muscle, fat, nerve cells)

Interphase • Longest phase of the cell cycle. • DNA is uncoiled. • 3

Interphase • Longest phase of the cell cycle. • DNA is uncoiled. • 3 stages: • Gap 1 (G 1): cell growth, organelles replicate • Synthesis (S): DNA is copied • Gap 2 (G 2): additional growth (prepare for mitosis)

Mitosis • Division of the nucleus • Has 4 stages – Prophase – Metaphase

Mitosis • Division of the nucleus • Has 4 stages – Prophase – Metaphase – Anaphase – Telophase • Produces 2 genetically identical daughter nuclei. • Occurs in somatic cells (all cells except sex cells)

Prophase • • • Longest phase of mitosis. Chromosomes condense. Nuclear membrane dissolves. Centrioles

Prophase • • • Longest phase of mitosis. Chromosomes condense. Nuclear membrane dissolves. Centrioles move to opposite ends of the cell Spindle fibers form, attach to chromosomes.

Metaphase • Chromosomes line up in the center of the cell.

Metaphase • Chromosomes line up in the center of the cell.

Anaphase • Sister chromatids separate, are pulled to opposite ends of the cell.

Anaphase • Sister chromatids separate, are pulled to opposite ends of the cell.

Telophase • Spindle fibers disintegrate. • Nuclear membrane forms. • Chromosomes begin to uncoil.

Telophase • Spindle fibers disintegrate. • Nuclear membrane forms. • Chromosomes begin to uncoil.

Cytokinesis • Cell pinches apart. • In plant cells, a cell plate forms (will

Cytokinesis • Cell pinches apart. • In plant cells, a cell plate forms (will become the cell wall).

Cells divide at different rates. • The rate of cell division varies with the

Cells divide at different rates. • The rate of cell division varies with the needs of the cell.

Cat s Summary of the Cell Cycle cat

Cat s Summary of the Cell Cycle cat

• Review: Cell Cycle Tutorials https: //www. youtube. com/watch? v=Jc. ZQkmooy. Pk •

• Review: Cell Cycle Tutorials https: //www. youtube. com/watch? v=Jc. ZQkmooy. Pk • Crash course: https: //www. youtube. com/watch? v=L 0 kenzoe. OM • http: //www. youtube. com/watch? v=VGV 3 fv-u. ZYI (shows centrioles and spindle fibers well) • Bozeman Science: http: //www. youtube. com/watch? v=1 c. VZBV 9 t. D-A

Practice Mitosis • http: //www. classzone. com/cz/books/bio_07/ get_chapter_group. htm? cin=2&ci=5&rg=anim ated_biology&at=animated_biology&npos=1& spos=5&var=animated_biology (practice, click

Practice Mitosis • http: //www. classzone. com/cz/books/bio_07/ get_chapter_group. htm? cin=2&ci=5&rg=anim ated_biology&at=animated_biology&npos=1& spos=5&var=animated_biology (practice, click on mitosis stage matching)