Chapter Ten Lecture- Mitosis

Copyright Pearson Prentice Hall

Biology


10–1 Cell Growth


Limits to Cell GrowthLarger cells demand more from their DNA and they have trouble moving enough nutrients and wastes across the cell membrane.


The rate of transport in and out of the cell is dependent on the surface area of the cell.The bigger a cell is the more nutrients it will need transported in and the more waste it will need transported out.


A cells volume increases faster than its surface area.This makes it more difficult for large cells to transport materials quickly enough for the cell to survive.



Before it becomes too large, a growing cell divides forming two “daughter” cells. The process by which a cell divides into two new daughter cells is called cell division.

Interphase is the period of growth that occurs between cell divisions.



10-2 Cell Division

Eukaryotic cell division occurs in two major stages. First, mitosis divides the cell nucleus. Second, cytokinesis divides the cell’s cytoplasm.


Chromosomes

Chromosomes

Genetic information is passed from one generation to the next on chromosomes.Before cell division, each chromosome is copied.

One copy two copies


Chromosomes

Each chromosome consists of two identical “sister” chromatids.Each pair of chromatids is attached at an area called the centromere.

Sister chromatids

Centromere


Chromosomes

When the cell divides, the chromatids separate.Each daughter cell gets one chromatid, so they have the same number of chromosomes as the parent cell.


The cell cycle is the series of events that cells go through as they grow and divide.

During the cell cycle:a cell growsprepares for divisiondivides to form two daughter cells, each of which begins the cycle again


The cell cycle has four phases:•G1 (First Gap Phase)•S Phase (DNA Synthesis)•G2 (Second Gap Phase)•M Phase (Mitosis)


During G1, the cell•increases in size•synthesizes new proteins and organelles


Events of the Cell Cycle

During the S phase,chromosomes are replicatedDNA synthesis takes place

Once a cell enters the S phase, it usually completes the rest of the cell cycle.


Events of the Cell Cycle

The G2 Phase (Second Gap Phase)

organelles and molecules required for cell division are producedOnce G2 is complete, the cell is ready to start the M phase—Mitosis

G1 + S + G2 = Interphase


Cell Cycle

Active art

Cell Division


Biologists divide mitosis into four phases:ProphaseMetaphaseAnaphaseTelophase


Mitosis

Mitosis

Mitosis movie


Prophase

Chromosomes (paired

chromatids)

Click to Continue

Spindle forming

Centromere


Prophase is the first and longest phase of mitosis.The centrioles separate and take up positions on opposite sides of the nucleus. Chromosomes

(paired chromatids)

Spindle forming

Centromere


The centrioles lie in a region called the centrosome.The centrosome helps to organize the spindle, a fanlike microtubule structure that helps separate the chromosomes. Chromosomes

(paired chromatids)

Spindle forming

Centromere


Chromatin condenses into chromosomes.The centrioles separate and a spindle begins to form.During prophase, the nuclear envelope breaks down.

Chromosomes(paired chromatids)

Spindle forming

Centromere


Centriole

CentrioleSpindle

Click to Continue

Metaphase


MetaphaseThe second phase of mitosis is metaphase.The chromosomes line up across the center of the cell.The centromere connects to the poles of the spindle.

Centriole

Spindle


Individual chromosomes

Anaphase


AnaphaseAnaphase is the third phase of mitosis.The sister chromatids are pulled apart by the spindle into two separate chromosomes.

Individualchromosomes


Nuclear envelope reforming

Telophase


TelophaseTelophase is the fourth and final phase of mitosis.Chromosomes gather at opposite ends of the cell and lose their distinct shape.


In telophase, a new nuclear envelope forms around each cluster of chromosomes.


Cytokinesis

Cytokinesis movie

Cytokinesis is not a part of mitosis.


During cytokinesis, the cytoplasm pinches in half.Each daughter cell has an identical set of duplicate chromosomes


In plants, a structure known as the cell plate forms midway between the divided nuclei.

Cell wallCell plate


The cell plate gradually develops into a separating membrane.A cell wall then begins to appear in the cell plate.


10-3 Regulating the Cell Cycle


Controls on Cell Division


Experiments show that normal cells will reproduce until they come into contact with other cells.When cells come into contact with other cells, they respond by not growing.This demonstrates that controls on cell growth and division can be turned on and off.



Contact Inhibition


Cell Cycle RegulatorsThe cell cycle is regulated by a specific protein.The amount of this protein in the cell rises and falls in time with the cell cycle. Scientists called this protein cyclin because it seemed to regulate the cell cycle. Cyclins regulate the timing of the cell cycle in eukaryotic cells.

A sample of cytoplasmis removed from a cellin mitosis.

The sample is injectedinto a second cell inG2 of interphase.

As result, the secondcell enters mitosis.

Cyclins were discovered during a similar experiment to this one.


Internal Regulators Proteins that respond to events inside the cell are called internal regulators.Internal regulators allow the cell cycle to proceed only when certain processes have happened inside the cell.


External Regulators Proteins that respond to events outside the cell are called external regulators.External regulators direct cells to speed up or slow down the cell cycle.

Uncontrolled Cell Growth

Cancer is a disorder in which some of the body's own cells lose the ability to control growth.

Cancer cells do not respond to the signals that regulate the growth of most cells.


Cancer cells divide uncontrollably and form masses of cells called tumors that can damage the surrounding tissues. Cancer cells may break loose from tumors and spread throughout the body, disrupting normal activities and causing serious medical problems or even death.

Practice questions are not part of the lecture notes, so you don’t need to copy them even though they are black.

Have a nice day! ☺


10–1

As a cell increases in size, which of the following increases most rapidly?

a. surface area

b. volume


10–1

If an imaginary cube-shaped cell has a length of 6 cm, its ratio of surface area to volume is

a. 1 : 1.

b. 6 : 1.

c. 36 : 1.

d. 1 : 6.


10–1

The process by which a cell divides into two new daughter cells is called

a. cell growth.

b. cell division.

c. DNA replication.

d. cell multiplication.


10–1

When one cell divides in two, what happens to the surface area to volume ratios in the new cells?a. There is no change in the amount of material

exchanged. b. Each new cell can exchange more material

than the original cell. c. Each new cell can exchange less material than

the original cell. d. The two new cells cannot be compared to the

original cell.


10–1

When a growing cell undergoes cell division, each new cell gets

a. half the DNA from the original cell.

b. twice as much DNA as the original cell.

c. a random sample of the DNA in the original cell.

d. a full copy of all the DNA in the original cell.


10-2

The series of events that cells go through as they grow and divide is called

a. the cell cycle.

b. mitosis.

c. interphase.

d. cytokinesis.


10-2

The phase of mitosis during which the chromosomes line up across the center of the cell is

a. prophase.

b. metaphase.

c. anaphase.

d. telophase.


10-2

Cytokinesis usually occurs

a. at the same time as telophase.

b. after telophase.

c. during interphase.

d. during anaphase


10-2

DNA replication takes place during the

a. S phase of the cell cycle.

b. G1 phase of the cell cycle.

c. G2 phase of the cell cycle.

d. M phase of the cell cycle.


10-2

During mitosis, “sister” chromatids separate from one another during

a. telophase.

b. interphase.

c. anaphase.

d. metaphase.


10-3

The cell cycle is believed to be controlled by proteins called

a. spindles.

b. cyclins.

c. regulators.

d. centrosomes.


10-3

Proteins that respond to events inside the cell are called

a. internal regulators.

b. external regulators.

c. cyclins.

d. growth factors.


10-3

Once a multicellular organism reaches adult size, the cells in its body

a. stop dividing.

b. grow and divide at different rates, depending on the type.

c. have the same life span between cell divisions.

d. undergo cell division randomly.


10-3

One effect of an internal regulator is that a cell will not begin mitosis until

a. it becomes too large.

b. the cell’s growth is stimulated.

c. it is in physical contact with other cells.

d. all its chromosomes have been replicated.


10-3

One factor common to almost all cancer cells is

a. a lack of cyclin.

b. a defect in gene p53.

c. exposure to tobacco smoke.

d. exposure to radiation.

Education

Chapter Ten Lecture- Mitosis