Cell Division and MitosisTB 174-180

What you will learn:

EXPLAIN why mitosis is important.

EXAMINE the steps of mitosis.

COMPARE mitosis in plant and animal cells.

LIST two examples of asexual reproduction

Why this is IMPORTANT

Your growth, like that of many organisms, depends on cell division

I. Why is cell division

important?Many organisms begin as one cell

Cell-division increases the total amount of cells in an organism

Even after growth stops, the body still needs cell division. Ex: red blood cells

Single-celled organisms use cell division to reproduce themselves

II. The Cell CycleLife Cycle begins with formation, followed by growth and development, and ends with death.

A. Length of Cycle (Fig. 2 pg.175)

• Series of events that takes place from one cell division to the next

• Time of life cycle varies with different cells

• Cells in humans that are needed for repair, growth, or replacement constantly repeat the cycle

II. The Cell CycleB. Interphase- period of cell growth and development

• Eukaryotic cell (cell with a nucleus)- spends most of cell cycle in Interphase

• Cells in the body that no longer divide (nerve/muscle) are always in Interphase

• Actively dividing cells copy hereditary material and prepares for division during Interphase

• DNA replication (copying) occurs during Interphase

WHY is it important to copy hereditary material?

• Before dividing, a copy of hereditary material MUST be made so new cells will have a copy

• Cells need the hereditary material to carry out life functions.

• After interphase, cell division begins

• Cell Cycle: https://www.youtube.com/watch?v=t2kBi1OWJdc

III. Mitosis and Cell Division

Process in which the nucleus divides to form 2 identical nuclei

Mitosis- series of steps

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

Anaphase—(Apart)

Prophase Metaphase (Middle)

Telophase—(Two)Anaphase—(Apart)

• 4 phases of nuclear division (mitosis), directed by the cell’s DNA (PMAT)

A. Steps of Mitosis

Chromosome- Structure in nucleus that contains heredity material

During Interphase, each chromosome duplicates

When nucleus is ready to divide, each duplicated chromosome coils tightly into 2 thickened, identical strands = Chromatids

III. Mitosis and Cell Division

A. Steps of Mitosis

• 1st Phase-Prophase

1. Nucleolus and nucleus membrane disintegrate

2. Centrioles (2 small structures)- move to opposite ends of cell

3. Between Centrioles, threadlike spindle fibers begin to stretch across the cell

** Plant cells form spindle fibers , but not Centrioles

III. Mitosis and Cell Division

· Chromosomes coil up

· Nuclear envelope disappears

· Spindle fibers form

Prophase

A. Steps of Mitosis

• 2nd Phase- Metaphase

Pairs of chromatids line up across center of cell

Centromere of each pair usually attaches to 2 spindle fibers- one from each side of cell

III. Mitosis and Cell Division

· Chromosomes line up in middle of cell

· Spindle fibers connect to chromosomes

Metaphase—(Middle)

A. Steps of Mitosis

• 3rd Phase- Anaphase

• Each Centromere divides and the spindle fibers shorten

• Each pair of chromatids separate, and chromatids move to opposite ends of cell

• Separated chromatids are now chromosomes

III. Mitosis and Cell Division

· Chromosome copies divide

· Spindle fibers pull chromosomes to opposite poles

Anaphase—(Apart)

A. Steps of Mitosis

• 3rd Phase- Telophase

• Spindle fibers start to disappear

• Chromosomes start to uncoil

• 2 nuclei form

• Cytoplasm begins to separate

III. Mitosis and Cell Division

· Chromosomes uncoil

· Nuclear envelopes form

· 2 new nuclei are formed

· Spindle fibers disappear

Telophase—(Two)

• Cytokinesis — the division of the rest of the cell (cytoplasm and organelles) after the nucleus divides

• In animal cells the cytoplasm pinches in

• In plant cells a cell plate forms

• After mitosis and cytokinesis, the cell returns to Interphase to continue to grow and perform regular cell activities (Figure 5 pg. 177)

III. Mitosis and Cell Division

MITOSIS- https://www.youtube.com/watch?v=C6hn3sA0ip0

MITOSIS Song- https://www.youtube.com/watch?v=I5uFuvkN97I

III. Mitosis and Cell Division

B. Results of Mitosis and Cell Division

Mitosis = the division of a nucleus

2 nuclei are identical to each other and to the original

Each new nucleus has the same number and type of chromosomes

The original cell no longer exists

Cell Division – replaces worn out or damaged cells

III. Mitosis and Cell Division

Cell Division Control• DNA controls all cell

activities including cell division

• Some cells lose their ability to control their rate of cell division – the DNA of these cells has become damaged or changed (mutated)

• These super-dividing cells form masses called tumors

• Benign tumors are not cancerous – these cells do not spread to other parts of the body

• Malignant tumors are cancerous – these cells break loose and can invade and destroy healthy tissue in other parts of the body (called metastasis)

Phase Chromosome Appearance & Location Important Events

Interphase

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

DNA replication, cell grows and replicates organellesNuclear envelope disappears, spindle fibers form

DNA copies itself; chromatin

Chromosomes coil up

Chromosomes line up in the middle

Spindle fibers connect to chromosomes

Chromosome copies divide and move apart

Spindle fibers pull chromosome copies apart to opposite poles

Chromosomes uncoil back into chromatin

Nuclear envelopes reform, 2 new nuclei are formed, spindle fibers disappearDivision of the rest of the cell: cytoplasm and organelles

Chromatin

IV. Asexual Reproduction2 Types of Reproduction

1. Sexual – Requires 2 organisms – hereditary material taken from both parents

2. Asexual – Requires 1 parent organism

• Asexual Reproduction = offspring produced will have hereditary material identical to parent organism

A. Cellular Asexual Reproduction

• Organisms with Eukaryotic cells reproduce by mitosis and cell division

A. Cellular Asexual Reproduction

• Types of Asexual Reproduction

1. Vegetative Propagation

• Occurs in plants

• Part of plant becomes separated from the parent plant and divides by mitosis

1. Stem = Runner – horizontal, running over soil surface

EX: Strawberry Plants

IV. Asexual Reproduction

A. Cellular Asexual Reproduction

• Types of Asexual Reproduction

2. Fission

• Bacterium does NOT have nucleus – Can’t use Mitosis

• 1-celled bacterium without nucleus copies genetic material and divides into 2 identical organisms

• https://www.youtube.com/watch?v=DY9DNWcqxI4

IV. Asexual Reproduction

A. Cellular Asexual Reproduction

• Types of Asexual Reproduction

3. Budding-

Figure 8A pg. 180

• New organism grows from the body of the parent organism

• Ex: Hydra

• Sometimes the bud on parent organism grows large enough, and breaks away to live on its own

• Others like sea coral grow and stay on the parent

• https://www.youtube.com/watch?v=a5oHMjGqjyo

IV. Asexual Reproduction

A. Cellular Asexual Reproduction

• Types of Asexual Reproduction

4. Regeneration-

• Process using mitosis and cell division to regrow body parts

• Figure 8B pg. 180

• If organism breaks into pieces, whole new organisms can grow from each piece

• Ex. Sponges and Sea Stars

• http://www.brainpop.com/science/cellularlifeandgenetics/asexualreproduction/preview.weml

IV. Asexual Reproduction