1

PowerPoint to accompany

CONCEPTS IN BIOLOGY

ELEVENTH EDITIONEnger • Ross

CHAPTER 8

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2

8.1 MITOSIS8.1 MITOSIS Cell division is essential to: Cell division is essential to:

Replace dead cells (50 million Replace dead cells (50 million

cells die per second)cells die per second) Repair damaged tissuesRepair damaged tissues GrowthGrowth Maintain the bodyMaintain the body

After a mitotic cell division, information After a mitotic cell division, information about the cell is equally distributed to about the cell is equally distributed to daughter cells.daughter cells.

3

8.2 THE CELL CYCLE8.2 THE CELL CYCLE All cells go through almost the same All cells go through almost the same

cell cycle. cell cycle. Even though we divide cell division Even though we divide cell division

into into 5 stages, once cell division starts it is 5 stages, once cell division starts it is a continuous process.a continuous process.

The five stages in cell division are:The five stages in cell division are:1.1. GG11——gap (growth) phase onegap (growth) phase one

2.2. SS——synthesissynthesis

3.3. GG22——gap (growth) phase twogap (growth) phase two

4.4. Cell division (mitosis and cytokinesis) Cell division (mitosis and cytokinesis)

5.5. GG00——gap (growth) mitotic dormancygap (growth) mitotic dormancy

4

5

THE CELL CYCLETHE CELL CYCLE

During the GDuring the G00 phase, cells are not in the phase, cells are not in the cell division cycle, they are cell division cycle, they are differentiated or specialized in their differentiated or specialized in their function.function.

Some cells remain in the GSome cells remain in the G00 phase (e.g., phase (e.g., nerve cells) and others get back to the nerve cells) and others get back to the cell cycle (Gcell cycle (G1 1 , S, and G, S, and G2 2 , e.g., bone , e.g., bone cells).cells).

The three phases GThe three phases G1 1 , S, and G, S, and G2 2 , occur , occur during the stage called interphase.during the stage called interphase.

6

7

THE CELL CYCLETHE CELL CYCLE During GDuring G11 phase cell growth, manufacture phase cell growth, manufacture

of tRNA, rRNA, enzymes cell components of tRNA, rRNA, enzymes cell components and enzymes are made.and enzymes are made.

DNA synthesis occurs during the S stage.DNA synthesis occurs during the S stage. Proteins required for the spindles are Proteins required for the spindles are

synthesized in the Gsynthesized in the G22 stage. During G stage. During G22 phase the cell prepares phase the cell prepares

to go through mitosis.to go through mitosis. At interphase, cells are engaged in their At interphase, cells are engaged in their

metabolic activities such as photosynthesis, metabolic activities such as photosynthesis, muscle cell contractions, and glandular-cell muscle cell contractions, and glandular-cell secretion.secretion.

8

8.3 STAGES OF MITOSIS8.3 STAGES OF MITOSIS

The stages of mitosis are:The stages of mitosis are:

1.1. ProphaseProphase

2.2. Metaphase Metaphase

3.3. Anaphase Anaphase

4.4. TelophaseTelophase

9

PROPHASEPROPHASE Prophase;Prophase; this is the first stage of this is the first stage of

mitosis and at this stagemitosis and at this stage:: Individual chromosomes become Individual chromosomes become

visible.visible. Nuclear membrane begins to Nuclear membrane begins to

disappear.disappear. Spindles begin to form.Spindles begin to form. The two identical chromatids are The two identical chromatids are

attached to the centromere.attached to the centromere. Centrioles move to opposite Centrioles move to opposite

poles.poles.

10

11

12

13

METAPHASEMETAPHASE Metaphase;Metaphase; is the second stage of mitosis, and is the second stage of mitosis, and

at this stage:at this stage: The nuclear membrane has The nuclear membrane has

disappeared.disappeared. Centrioles are at opposite poles.Centrioles are at opposite poles. Chromosomes are aligned at Chromosomes are aligned at

equatorial plane.equatorial plane. Each chromosome still has two Each chromosome still has two

chromatids. chromatids. In human cells there are 46 In human cells there are 46

chromosomes, (each with two chromosomes, (each with two chromatids) or 92 chromatids.chromatids) or 92 chromatids.

Chromosomes are attached to the Chromosomes are attached to the spindle.spindle.

14

15

16

ANAPHASEANAPHASE Anaphase is the third stage of mitosis Anaphase is the third stage of mitosis

and at this stage:and at this stage: Centromeres split and chromatids Centromeres split and chromatids

separate.separate. Chromatids are also called Chromatids are also called

daughter chromosomes.daughter chromosomes. Chromatids move to opposite Chromatids move to opposite

poles by a motor protein poles by a motor protein (kinetochore).(kinetochore).

Each chromatid moving to the Each chromatid moving to the opposite pole is the exact copy of opposite pole is the exact copy of the other.the other.

17

18

TELOPHASETELOPHASE Telophase is the last stage of mitosis and at this Telophase is the last stage of mitosis and at this

stage:stage: Cytokinesis or equal division of the cell Cytokinesis or equal division of the cell

cytoplasm takes place.cytoplasm takes place. Each set of chromosomes unwinds.Each set of chromosomes unwinds. Nuclear membrane reappears and Nuclear membrane reappears and

chromosomes are enclosed in it.chromosomes are enclosed in it. Nucleoli of the cell reappears.Nucleoli of the cell reappears. Each of the daughter cells formed now Each of the daughter cells formed now

enter Genter G11 stage of interphase. stage of interphase. The cells grow and enter another cycle The cells grow and enter another cycle

of mitosis.of mitosis.

19

20

21

8.4 PLANT AND ANIMAL CELL 8.4 PLANT AND ANIMAL CELL DIFFERENCESDIFFERENCES

For the most part, animal and plant cells For the most part, animal and plant cells have very similar cell division cycles.have very similar cell division cycles.

Among the differences are:Among the differences are: Plant cells do not have centrioles, but Plant cells do not have centrioles, but

somehow are able to produce a somehow are able to produce a spindle.spindle.

There is a difference in the process of There is a difference in the process of cytokinesis, in animal cells form a cytokinesis, in animal cells form a cleavage furrow and in plants a cell cleavage furrow and in plants a cell plate is formed.plate is formed.

22

23

24

25

8.5 DIFFERENTIATION8.5 DIFFERENTIATION Even though all cells originate from a set Even though all cells originate from a set

of genes from your father in his sperm, of genes from your father in his sperm, and a set of genes from your mother in and a set of genes from your mother in her egg, they are all the same genes in her egg, they are all the same genes in your body except for mutations.your body except for mutations.

All cells in the body are genetically All cells in the body are genetically identical but have different functions, identical but have different functions, e.g., nerve cells, muscle cells, red blood e.g., nerve cells, muscle cells, red blood cells . . . each with a specific function.cells . . . each with a specific function.

The process of creating these specialized The process of creating these specialized cells is called cell differentiation.cells is called cell differentiation.

26

STEM CELLSSTEM CELLS Stem cells are cells that can become Stem cells are cells that can become

any cell type. any cell type. Stem cells found in the bone marrow Stem cells found in the bone marrow

can be differentiated and become any can be differentiated and become any cell cell e.g., red blood cells, nerve cells . . . e.g., red blood cells, nerve cells . . .

The reason that bone marrow The reason that bone marrow transplants are used to cure certain transplants are used to cure certain diseases is because the stem cells can diseases is because the stem cells can differentiate to obtain the desired cells. differentiate to obtain the desired cells.

27

28

29

30

31

32

33

34

35

36

37

38

39

40