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Do Now: What process do you think this cartoon is describing?

Mitosis: Cell Division

Key Points On Cell Division

� Species must reproduce in order to survive from generation to generation.

� All living things reproduce by cells dividing called cell division.

� Cell division allows for growth and reproduction.

� Also, helps to replace old and damaged cells.

� To maintain the surface area for the given volumeof each cell’s growth. Ex: a balloon

Cell Division: A Basic Fact of Life

Every living creature from

bacterium

to whales

and to trees

results from cell division!

Mitosis� Two types of cell division are mitosis & meiosis.

� In mitosis, body cells called somatic cells go through cell division. These cells are nonsex cells.

� The uncontrollable cell division of certain abnormal

cell is referred to as cancer.

Mitosis (mitotic cell division)

� Mitosis is a series of changes in the nuclei of all body cells.

� Therefore, reproduction occurs in the nucleus.

� Chromosomes replicate then parent cell divides.

� Parent divides into 2 daughter cells.

� Both daughter cells have the same # of chromosomes as the parent.

� The number of chromosomes is 46 (2n).

2

46

46 46

2 Daughter Cells

2N

2N 2N

DNA

replication

Mitosis

2 Diploid daughter cells

46Chromosomes

46

46

46 46

46 Words To Know

� Nucleus

� Chromatin

� Chromosomes

� Centrioles

� Centromeres

� Poles

� Spindle fibers

� Equatorial plate

� Cytokinesis

� Nucleus- Contains hereditary material called

chromosomes.

� Chromatin- Thin twisted threads made of DNA. - Found during non-dividing cells.

� Chromosomes- Thickened & coiled chromosome made of DNA

- Found during dividing cells (mitosis).

Genetic Material In Mitosis

Replicated

Chromosome

2 Chromatidseach with a double helix

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Replicated Chromosome

2 Chromatids each with a double helix

http://bcs.whfreeman.com/thelifewire/content/chp11/1102002.html

Structures seen during Mitosis

� Centrioles- Two tiny football shaped bodies that make

spindle fibers to pull double chromosome apart.

� Centromere (button)- Connect the chromatids in the center.

Draw &

Label A.

B.C.

� Poles

- The opposite ends of the cell.

� Spindles fibers

- Fibers that help move chromosomes during cell division. Spindle

Poles

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Equatorial plate

� Region where the chromatids reach the center of the cell.

Equatorial

Plate

Cytokinesis

- Cytoplasm divides into two parts.

- Each part has its’ own nuclei & a

complete set of hereditary material

(DNA).

The Process of Cytokinesis

Cleavage- the tightening and

pulling of protein

Nucleus

Microtubules

The Cell Cycle

What Does “Cell Cycle” Mean?

� The repetitive process that cells undergo

for cellular growth and reproduction.

� Cell cycle has 2 phases.

Interphase Mitosis

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� Different cells vary in the time they spend in interphase and mitosis.

Ex: Nerve cells can spend up to 60 years in

interphase and so rarely reproduce. This is why spinal cord injuries and stroke patients have permanent damage.

Nerve Cells Cancer Cells

� Cancer cells are never

at rest and remain a short time in interphase

and so cells

keep dividing.

Cell Cycle: Interphase + Mitosis

� A human cell can divide (go through mitosis) in 1 hour.

� Cells in the interphase period can remain for 16-20 hours.

Cell is synthesizing its structural proteins and enzymes

chromosome is copied to be 92.

Or each

Prepares for mitosis

The Phases of Mitosis

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

“PMAT”

Cell Cycle: Interphase + Mitosis

� Interphase is not considered part of mitosis(division stage).

� Interphase is the period before mitosis

begins.

Mitosis and Cell Reproduction

Looking At The Cellular

Level

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The Phases of Mitosis

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

Cytokinesis

“PMATc”Let’s Draw The

Phases of Mitosis

Use Board

Interphase &

Mitosis In

Animal Cells

46

Chromosomes

4646

Chromosomes

Doubled to 92

Middle

Apart

Interphase � Chromosomes long,

thin, thread-like & not visible in the nucleus.

� Uncoiled DNA is called chromatin. Each makes a copy of

itself (replication).

� Centrioles form.

http://www.cellsalive.com/cell_cycle.htm

Prophase� Chromosomes thicken

& can see under microscope.

� Nuclear membranedisappears.

� Spindle fibers form.

� Centrioles move to opposite sides.

� Centromeres holdchromosomes together.

ChromatidsCentromere

CentriolesSpindle

fibers

Metaphase

� M = MIDDLE

� Double chromosomes

line up in the middle

of the cell by the spindle fibers.

Metaphase plate

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Anaphase

� Spindle fibers

shorten & pull apart(separate).

� Chromatids become

single-stranded

chromosomes as they

move to opposite sides.

Telophase &Cytokinesis

Telophase� Chromosomes uncoil

into chromatin.

� Nucleolus & nuclear membraneform again.

Cytokinesis- Pinching of the cell &

cytoplasm divides.

� Two new daughtercells form & each is identical to the original.

46

46

The first stage of mitosis when chromosomes

start becoming visible in the microscopeis called:

A. anaphase

B. prophase

C. telophase

D. metaphase

Prior to cell division, each chromosome replicates or duplicates its genetic material. The products are

connected by a centromere and are called:

A. sister chromosomes

B.homologous

chromosomes

C. sex chromosomes

D. sister chromatids

Which of the following statements is

NOT true of mitosis?

A.

A single nucleus gives rise to two identical daughter nuclei.

B

.The daughter nuclei are genetically identical to the parent nucleus.

C

.The centromeres divide at the onset of anaphase.

D

.Homologous chromosomes synapse in prophase.

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MitosisIn Plant Cells

Plant Cells

�Mitosis can be seen in developing seeds, the roots, and stems.

�Same nuclear division occurs in

both plant cells and animal cells.

How Does Mitosis Differ In Plants?

1. No centrioles.

2. A cell plate forms between 2 daughter cells. So no pinching

occurs.

Cell Plate

No Centrioles

Which of the following features of cell division

are very different for animal and plant cells?

A. prophase

B. metaphase

C. anaphase

D. cytokinesis

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Cytokinesis in a plant cell is

characterized by:

Athe equal division of homologous

chromosomes.

Ba pinching off of the cell membrane to

divide the cell.

Cthe formation of a cell plate in the

cytoplasm.

Dthe movement of the chromosomes

from the metaphase plate.