Friday Feb 10th Day E

• Collect remaining Wequests• Begin 10.2

– Notes– Video Clip– Handout

HW – Study for 10.1 QuizChapter 10 VocabularySurface area/volume problems

Chapter 10.2Chapter 10.2Cell Division

Cell Division

• Before a cell gets too large, a growing cell divides forming two “daughter cells”

• Cell division process by which a cell divides into two new daughter cells

• Before cell division begins, DNA replicates (copies) itselfOne copy for each new cell

Division in Prokaryotes• After DNA is copied, cell splits in two

Each new cell contains a copy of the DNA called binary fissionbinary fission– Example of asexual reproduction

Binary Fission in a Paramecium

Division in Eukaryotes

• Occurs in two main stages– 1st stage division of the nucleus = mitosis– 2nd stage division of the cytoplasm = cytokinesis

• Helps multicellular organisms grow and develop

Chromosomes Structures that carry genetic information

– Made up of DNA and protein (histones)

• Humans have 46 total (23 pairs) (other organisms have different numbers)

Chromosomes• While the cell is “resting”, you cannot see the

chromosomes. It is unwoundCalled chromatin

chromatin chromosome

(1) Double-stranded DNA. (2) Chromatin strand (DNA with histones). (3) Chromatin during interphase with centromere. (4) Condensed chromatin during prophase. (Two copies of the DNA molecule are now present) (5) Chromosome during metaphase.

Chromosomes• While the cell is dividing, you can see the

chromosomes It is wound upMade of two sister chromatids connected by a

centromere

Chromosomes

Centromere

Sister Chromatid

The Cell Cycle• Occurs in eukaryotic

cells

It is the period of time from the beginning of one cell division to the beginning of the next

• Cell doubles its contents so that it is ready to divide into two completely independent cells

M phase

S phase

G1 phase

G2 phase

The Cell Cycle

Consists of 4 phases – 1. M phase – mitosis the division of the cell nucleus and cytokinesis– 2. G1 intense growth and activity; new proteins and organelles are made– 3. S phase copying of chromosomes– 4. G2 intense growth and activity; new proteins and organelles are made

• Shortest of the four phases

M phase

S phase

G1 phase

G2 phase

M phase

• Cell division– Process in which the cell divides

into two independent cells daughter cellsdaughter cells

– Process is called mitosismitosis in eukaryotes and binary fissionbinary fission in prokaryotes

Cell Cycle Rates

Cells do not move through the cell cycle at the same rate– Average rate of a human cell is once every 20

hours

Mitosis

• Time of cell division

• Divided into four main phases– 1. Prophase– 2. Metaphase– 3. Anaphase– 4. Telophase

Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2Mitosis and Cytokinesis

1. Prophase• 1. Appearance of chromosomes

– 2 sister chromatids attached at the centromere

• 2. Nuclear membrane begins to breakdown

• 3. Spindle begins to form– Purpose is to pull chromatids apart

• 4. Spindle attaches to the chromosomes at the centromere– In animals, spindle is made by the centriole

Plants lack centrioles

Spindle forming

Centromere

Chromosomes (paired chromatids)

2. Metaphase

• 1. Chromosomes line up in the middle of the cell

Centriole

Centriole

Spindle

3. Anaphase

• 1. Centromeres split

• 2. Sister chromatids are pulled to the opposite ends of the cell by the spindle

Individual chromosomes

4. Telophase

• 1. Spindle breaks down

• 2. Nuclear envelope reforms around the chromosomes

• 3. Chromosomes unwind to chromatin again

Nuclear envelope reforming

Cytokinesis• Division of the cytoplasm

• In animals the cell pinches in at the middle to create two new cells

• In plants a cell plate is created in the middle of the cell

Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2Mitosis and Cytokinesis

Videos

• Animal Cell Mitosis

• Animal Cell Cytokinesis

• Animal Cell Mitosis: Interactive

• How the Cell Cycle Works

Friday Feb 10th Day E

• Collect remaining Wequests• Begin 10.2

– Notes– Video Clip– Handout

HW – Study for 10.1 QuizChapter 10 VocabularySurface area/volume problems