CELL CYCLE and MITOSIS Why do cells reproduce

CELL CYCLE and MITOSIS Why do cells reproduce? How do cells reproduce? What controls cell division? What is the relationship between mitosis and tumors?

Why do cells need to divide? Some organisms divide in order to reproduce (asexual reproduction) • Organisms like humans rely upon cell division in order to grow, and to replace old or damaged cells •

Cell Division in Sexually Reproducing Organisms Sexually reproducing organisms use cell division to make more cells that are genetically identical.

How Do Cells Reproduce? The Cell Cycle • Overview of Cell Cycle: The cycle of activities that a cell undergoes during its lifetime. • New cells start in interphase • Consists of: • Interphase (not dividing) • M Phase (dividing) •

Cell Cycle includes G 1 phase Go to Section: Interphase M phase (Mitosis) is divided into S phase G 2 phase Prophase Metaphase Anaphase Telophase

The Cell Cycle Interphase, the longest phase, (~90% of cycle) • The cell: • grows and carries out normal functions (G 1 phase) • prepares for mitosis, or cell division: • DNA is replicated (S Phase): now each chromosome is “duplicated chromosomes” (two sister chromatids) • organelles including centrioles replicate (G 2 phase) •

The Cell Cycle: Mitosis Duplicated Cs.

Cell Cycle DNA Polymerase

Interphase

Mitosis Vocabulary 1. Cell Division: 1. Mitosis - the first stage of cell division when the nucleus divides 2. Cytokinesis – the second stage of cell division, when the cytoplasm divide 2. Parent cell - the cell that is dividing 3. Daughter cells- the two new cells that form from mitosis

Mitosis Vocabulary 4. Centriole - a small structure located near the nucleus; it creates the spindle (in animal cells only) 5. Spindle - a fibrous, oval-shaped structure formed by the centrioles during mitosis

Mitosis Vocabulary 6. Chromosomes (DNA threads) – genetic material within the cell that controls the cell’s activities. 7. Chromatids – sister strands of a replicated chromosome attached at the centromere. 8. Centromere - the area (near the middle) where sister chromatids are attached to each other.

Figure 12. 3 Chromosome duplication and distribution during mitosis

Cell Cycle: Mitosis (Nuclear division) l Mitosis—the process by which the nucleus of a parent cell is divided into two identical nuclei, which makes two new identical daughter cells. l Each of the daughter cell nuclei has the same number and kinds of chromosomes as the parent cell. • Chromosome – long strand of DNA wound around proteins. (Humans have 23 pairs = 46 total)

Sister chromatids have identical DNA!

Cell Cycle: Mitosis (Nuclear division) l Divided into 4 phases: ¡ 1. Prophase ¡ 2. Metaphase ¡ 3. Anaphase ¡ 4. Telophase with cytokinesis M phase

Mitosis Animation https: //highered. mcgrawhill. com/sites/0072495855/student_view 0/chapter 2/animation__ mitosis_and_cytokinesi s. html

Prophase • • Replicated chromosomes become shorter and thicker (condensed) – look like X’s Nuclear membrane fragments and goes away Centrioles begin to separate The spindle (tiny threads) forms between the centrioles

Prophase

Metaphase (line up in Middle) • • • Centrioles finish separating and the spindle is completely formed The replicated chromosomes line up SINGLE FILE in the middle of the cell Spindle fibers still attached to the center of each chromatid and radiate out

Metaphase

Anaphase (sister chromatids pull Apart) • • • Sister chromatids separate as spindle fibers pull them apart One set moves to each end of the cell Ends when the chromatids have formed two groups near each side of the cell

Anaphase

Telophase (makes Two new cells) • • The nuclear membrane reforms around each nucleus The spindle disappears Chromosomes become longer and thinner and are no longer visible One cell separates into two identical cells (cytokinesis)

Telophase

Cytokinesis • Cell membrane pinches in (animal cells only) and forms two cells

Mitosis in Plant Cells § § Plants have no centriole, but the spindle still develops Plant cell cytoplasm separates into two parts by the formation of a cell plate. This becomes the cell wall of the new plant cells.

Mitosis Activity l Put the diagrams of mitosis in order

See what you know! The following are different stages of mitosis. See if you can identify what stage the cell is in.

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Homework Pretend you are small enough to hitch a ride on a chromosome in a plant cell • Describe what you would see as the cell goes through the cell cycle • Start with interphase and end with cytokinesis •

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