CELL DIVISION

Why do cells Divide?

For Growth Development Repair Reproduction

Larger cells:

- can miscommunication with DNA

- have trouble processing information

- struggle to exchange materials

across the membrane (SA:V)

Cell Division

Two Types of reproductionAsexual Reproduction

○ Genetically identical offspring from a single parent’s cells dividing

Sexual Reproduction○ Fusion of sex cells from 2

individuals

Advantages of Reproduction Types Asexual: Survival Strategy for single celled

organismsOffspring are genetically identical to parent.Occurs rapidly under favorable conditions.Lower energy input

Sexual: Survival Strategy for multi-cellular organismsOffspring are genetically varied from parentAn advantage in environments that change

frequentlyHigher energy input

Cell Division

A single cell divides into 2 daughter cells

The Cell Cycle

A Series of steps a cell goes through

Growth of the cell / parts Synthesis of new DNA Division of the cell

Cell Division

The Beginning of the Cycle is called Interphase G1- intense growth and making of

new proteins and organelles S - new DNA is synthesized so 2

copies of the chromosomes exist G2 – Preparation and replicating

organelles

The Cell Cycle

A Series of steps a cell goes through:

-growth, preparation, division

B. Prokaryotes:

- asexual reproduction called

binary fission

C. Eukaryotes

- Four phases: G1, S, G2, and M

The Cell Cycle

The Second Stage in the cycle is Mitosis

(division of nucleus and cytoplasm)

III. Chromosomes

A. Packages of DNA (genetic information) that is bundled together.

centromere

chromatids

Duplicated chromosome

Chromosomes (cont.)

B. Prokaryotes-Contain single, circular chromosome.

Bacterial chromosome plasmids

Chromosomes (cont)C. Eukaryotes

-contain multiple chromosomes

-Chromatin -DNA is generally

wrapped around proteins called

histones.

Counting Chromosomes

Chromosomes can have one or two sets of DNA.

Count chromosomes by counting the number of centromeres

a. Mitosis

Prophase –

1. genetic material

condenses

2. chromosomes become

visible

3. spindle starts to form

4. nuclear envelope

disappears

Mitosis (cont.)

Metaphase –

1. Duplicated chromosomes line up in middle

2. Spindle fibers connect to centromeres

Mitosis (cont)

Anaphase –

1. Sister chromatids separate and move to opposite ends of the cell

Mitosis (cont)

Telophase

1. Condensed chromosomes begin to spread out into chromatin.

2. Nuclear envelope

re-forms

b. Cytokinesis

-division of the cytoplasm

-splits parent cell into identical 2 daughter cells

Cytokinesis (cont)Animal Cells: membrane pinches inward

Plant Cells: cell plate develops from inside

Cell Division Animation

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_cell_cycle_works.html