Chapter 4: Cell Reproduction

Section 1: Cell Division and Mitosis

Mr. MotukMinersville Area Jr./Sr. High School

Section 1: The Cell Cycle (1) 2

I. Cell CycleA. Cell Cycle: Organisms to through stages, or a life cycle,

while they are alive. 1. A simple life cycle would be birth, growth and

development, and death. 2. Cells go through a life cycle.

a. The cell cycle is a series of events that take place in a cell from one division to the next.

b. Different types of cells divide differentlyi. Nerve cells cannot be replaced while skin cells are

constantly being replaced.

Section 1: The Cell Cycle (1) 3

I. Cell CycleB. Steps of the Cell Cycle- The cell cycle is a series of events

that cells go through as they grow and divide. 1. Interphase, Prophase, Metaphase, Anaphase, Telophase,

and Cytokenesis.

C. INTERPHASE- First step in the Cell Cycle has three parts. 1. G1 Phase

a. During the G1 phase cells do most of their growing. b. During this phase, cells increase in size and synthesize

(make) new proteins and organelles.

Section 1: The Cell Cycle (1) 4

I. Cell CycleC. Interphase (Continued)

2. S-Phasea. The G1 Phase is followed by the S Phaseb. Chromosomes are replicated and the synthesis of DNA

occurs.3. G2 Phase

a. G2 is usually the shortest phase of interphase. b. During G2 phase, many of the organelles and

molecules required for cell division are produced. c. When the events of the G2 Phase are complete, the

cell is ready to enter the Mitosis and cytokinesis phases, and begin the process of cell division.

Section 1: The Cell Cycle (1) 5

Section 1: The Cell Cycle (1) 6

Cell Cycle: Time breakdown

Section 1: The Cell Cycle (1) 7

Duplication of Chromosomes

Section 1: The Cell Cycle (1) 8

I. Cell CycleD. Mitosis- Biologists divide the events of Mitosis into four

phases: prophase, metaphase, anaphase, and telophase; Mitosis is the process in which the nucleus divides to form two identical nuclei. 1. Prophase- First and longest phase of mitosis.

a. Chromosomes become visible. b. Centrioles separate and locate on opposite sides of the

nucleus. c. Between the centrioles threadlike spindle fibers begin to

stretch across the cell. d. Nuclear membrane and nucleolus fade and disappear.

Section 1: The Cell Cycle (1) 9

Section 1: The Cell Cycle (1) 10

2. Metaphase a. The chromosomes

line up across the center of the cell.

b. Each chromosome is connected to a spindle fiber at its centromere.

Section 1: The Cell Cycle (1) 11

2. Anaphasea. Each centromere

divides. b. The two strands of

each chromosome separate.

c. The separate strands begin to move towards opposite ends of the cell.

Section 1: The Cell Cycle (1) 12

I. Cell CycleD. Mitosis- (Continued)

4. Telophasea. The final step of mitosis. b. Centrioles and spindle fibers

start to disappear. c. Chromosomes stretch out and

become harder to see. d. Nuclear membrane from

around each mass of chromosomes.

e. New nucleolus appears in each nucleus.

Section 1: The Cell Cycle (1)

I. Cell CycleE. Cytokinesis

1. Cell membrane pinches the cytoplasm in half.

2. Each daughter cell has an identical set of duplicate chromosomes. a. In plants, a structure known

as the cell plate forms midway between the divided nuclei.

b. The cell plate gradually develops into a separating membrane.

c. A cell wall then begins to appear in the cell plate.

13

Section 1: The Cell Cycle (1) 14

I. Cell CycleF. Results of Mitosis

1. Mitosis is the division of the nucleus, it produces two nuclei that are identical to each other and the original nucleus.

2. Each cell in your body, except sex cells, has a nucleus with 46 chromosomes, 23 pairs.

3. All of your cells use different parts of the same hereditary material to become different types of cells. (see pg 100 in your book)

Section 1: The Cell Cycle (1) 15

I. Cell CycleF. Results of Mitosis

4. Mitosis allows growth and replaces worn out or damaged cells.

a. If you cut yourself, the wound heals because cell division replaces damaged cells.

b. You are much larger and have more cells than a baby mainly because of cell division.

Section 1: The Cell Cycle (1) 16

Cell Type Life Span Cell Division

Lining of Esophogus 2-3 days Can divide

Lining of small intestine 1-2 days Can divide

Large Intestine 6 days Can divide

Red Blood Cells Less than 120 days Cannot divide

White Blood Cells 10 hours to decades Cannot divide

Smooth Muscle Long lived Can divide

Cardiac Muscle Long lived Cannot divide

Skeletal Muscle Long Lived Cannot divide

Neuron (nerve cell) Long Lived Cannot divide

Section 1: The Cell Cycle (1) 17

II. Asexual ReproductionA. Asexual Reproduction

1. There are two types of reproduction. a. Asexual reproductionb. Sexual reproduction

2. In asexual reproduction, a new organism (sometimes more than one) is produced from one organism.

a. The new organism will have hereditary material identical to the hereditary material of the parent organism.

b. How many organisms are needed for asexual reproduction?i. One

Section 1: The Cell Cycle (1) 18

II Asexual Reproduction

B. Cellular Asexual Reproduction

1. Organisms with eukaryotic cells (have a nucleus) asexually reproduce by cell division.

a. New strawberry plants can be reproduced asexually from horizontal stems called runners.

Section 1: The Cell Cycle (1) 19

II Asexual Reproduction

B. Cellular Asexual Reproduction

Section 1: The Cell Cycle (1) 20

II. Asexual Reproduction

B. Cellular Asexual Reproduction2. Bacteria do not have a nucleus, so they

cannot use mitosis. a. Instead bacteria reproduce asexually by

fission. b. During fission, an organism whose cells do

not contain a nucleus copies its genetic material and then divides into two identical organisms.

Section 1: The Cell Cycle (1) 21

II. Asexual ReproductionB. Cellular Asexual

Reproduction3. Budding

a. Budding is a type of asexual reproduction made possible because of cell division.

b. When the bud on the adult becomes large enough, it breaks away to live on its own.

Section 1: The Cell Cycle (1) 22

II. Asexual ReproductionB. Cellular Asexual Reproduction

4. Regeneration – The process that uses cell decision to re-grow body parts.

a. Sponges, planaria, sea stars, and some other organism can use regeneration for asexual

reproduction. b. Because sea stars eat oysters, oyster farmers dislike

them.

Section 1: The Cell Cycle (1) 23