Cell Cycle and Cell DivisionChapter 9

Cellular ReproductionChapter 9 Slides

Part 1Text Pages 244-257

Warm-up Questions

• How would you describe the process by which organisms increase in size?

• Are the cells of a small plant smaller or larger than those of a large plant?

• Why do you think cells stay small?• http://www.cellsalive.com/howbig.htm

Surface area must allow for adequate exchange of materials.Otherwise, the cell would die because it is unable to

Import needed materials and export wastes.

When do cells divide?

Cells grow and function normally until they become too large. Cell size is limited because volume increases faster than surface area.

This means that there is not enough area on the surface of thecell to bring in the amount of nutrients needed for the growing volume of the cell.

Three Reasons Why Cells Divide:

1. Growth

2. Replace

3. Repair

Where you listening??

Why do cells divide?1.Growth2.Replace

3.Repair

THE CELL CYCLE: - the series of events that cells go through as

they grow and divide. - During the cell cycle, a cell:

- grows- prepares for division- divides into two

daughter cells

Once a cell reaches its size limit, it either stops growing or it divides.

Before the cell can begin the division phase of thecell cycle, the DNA located within must be condensed.

Why is it important for DNA to condense?

• Condensing makes it easier to move DNA around the cell.

• Just like when you travel, you pack everything in a suitcase.

DNA doublehelix

DNA andhistones

Chromatin SupercoiledDNA

• Chromosomes condense at the start of mitosis.

- DNA wraps around proteins called histones which are similar to beads on a string.

- This forms chromatin, a combination of DNA and proteins- The chromatin then condenses into small thick rods of supercoiled DNA.

Making sense of DNA terms…

• DNA is usually in the form of chromatin = relaxed form of DNA

• Before the cell divides, DNA is duplicated to form sister chromatids.

• The centromere holds chromatids together.

• Then DNA organizes into chromosomes.

Condensed, duplicated chromosome

chromatid

chromatid

centromere

telomere

• Telomeres protect the ends of the chromosomes and help prevent the loss of genes.

There are two types of cells...so there are two types of cell division

Prokaryotic cells do BINARY FISSION: 1.DNA is copied 2.Cell divides3. Each new cell has an

identical DNA copy.

•In eukaryotic cells, it’s more complex…

Preparing for Cell Division

Cell Division in Eukaryotes is Called

MITOSISMitosis is part of the Cell Cycle

Eukaryotic Cell Cycle: Overview 1. Interphase:

when cell grows and

prepares to divide

2. Mitosis: when

nucleus divides

3. Cytokinesis: when cytoplasm divides and two new cells are complete

The Cell Cycle

3 main Stages or phases:

1. Interphase2. Mitosis3. Cytokinesis

Interphase

• Three parts to interphase.– G1– S– G2

Interphase (G1 phase)

“Growth 1” = making proteins and organelles

(“inter” = between)

Interphase (S phase)

“Synthesis”= replication of DNA

(sister chromatids form)

Interphase (G2 phase)

“Growth 2”= cell takes inventory to prepare for mitosis

Mitosis

• 4 stages– Prophase– Metaphase– Anaphase– Telophase

PMAT or Please Make Another Taco

Prophase• DNA and proteins condense into tightly coiled chromosomes

• The nuclear envelope breaks down

• Centrioles begin to move to opposite poles

• Spindle fibers form

Which of these is in prophase?

A

C

D

E

B

• Chromosomes line up in the middle of the cell

Metaphase• Spindle fibers attach to each chromosome at the centromere

Which of these is metaphase?

A

C

D

E

B

Anaphase• Sister chromatids separate to opposite sides of the cell

• Spindle fibers begin to shorten, which pulls the sister chromatids away from each other

Which of these is in anaphase?

A

C

D

E

B

Telophase • Nuclear membranes start to reform around each identical set of chromosomes.

• Chromosomes begin to uncoil.

• Spindle fibers fall apart.

• Mitosis Ends

Which of these is in telophase?

A

C

D

E

B

Cytokinesis

• Cytoplasm and cell contents divide

• Division of cell into two, identical cells called daughter cells

• Daughter cells have the same # of chromosomes as each other and as the parent cell from which they were formed

Animation:

Warm-up

Name the three main phases of the Cell Cycle:

Name the three stages of Interphase:

Name the four stages of Mitosis:

Cytokinesis• Cytokinesis is the division of the cytoplasm

Cytokinesis differs in animal and plant cells:• In animal cells, the membrane pinches closed to form a Cleavage Furrow.

• In plant cells, a cell plate forms between the two nuclei

Animal cell mitosis

Plant cell mitosis

Cytokinesis differs…

CELL PLATE

Quia Vocab Practice

• http://www.quia.com/jfc/2513896.html?AP_rand=539735680

Warm-up1. Chromosomes condense and the nuclear

membrane dissolves during the ____________ phase of mitosis.

2. Chromosomes line up in the middle of the cell during _________________.

3. Sister chromatids are pulled apart during ___________.

4. Nuclear membrane reforms and chromosomes de-condense during ________.

Pages for Reference

• Pages 244 – 252 in the textbook• Cell Cycle on page 246• Stages of Mitosis on page 249• Guided Notes for Chromosome

structure