Chapter 8.5

Question 1

examples of cells that constantly divide

Answer 1

1. the cells at the tip of plant’s roots

2. stems cells in bone marrow continue to produce new blood clls

Question 2

egs of cells that stop dividing

Answer 2

1, skin cells around a wound stop dividing once the healing is complete
2. brain cells rarely divide once they mature

Question 3

What two groups of proteins guide a cell’s progress through the cell cycle

Answer 3

Cyclin : fluctuate in predictable ways during each stage:
2. proteins that bind to each cyclin: translate these fluctuations into action by activating the transcription factors that stimulate entry into the next stage of the cell cycle

Question 4

The interactions of the signaling proteins ( cyclin and the proteins that bind to it)serve as what

Answer 4

checpoints : they ensure that cello does not enter one stage until the previous stage is complete

Question 5

What are the mechanics of the checkpoints of the cell cycle

Answer 5

A cell that fails to pass a checkpoint correctly will not undergo the change in cyclin concentrations that allow it to progress to the next stage

Question 6

G1 checkpoint

Answer 6

screens for dna damage

Question 7

S phase checkpoints

Answer 7

ensures that dan replication occurs properly

Question 8

G2 checkpoint

Answer 8

Is the last point before the cells begins mitosis

Question 9

metaphase checkpoint

Answer 9

ensures that all chromosomes are aligned and that the the spindle fibres attach correctly to the chromosomes

Question 10

Why are checkpoint timing essential

Answer 10

too little cell division - an injury would go unprepared

Too much Cell division: an abnormal growth forms

Question 11

TUMOR

Answer 11

an abnormal mass of tissue

Question 12

2 types of TUMORS

Answer 12

1. BENIGN TUMORS

2. MALIGNANT TUMORS

Question 13

BENIGN TUMORS

Answer 13

usually slow growing and harmless, unless they get large enough to disrupt nearby tissues or organs

Question 14

What prevents a tumor from spreading

Answer 14

a tough capsule of connecting tissue surrounding the tumor

Question 15

egs of benign tumors

Answer 15

warts and moles

Question 16

MALIGNANT TUMORS

Answer 16

1. invades adjacent tissue

Question 17

why do malignant tumors spread

Answer 17

because it lacks a surrounding capsule, making it likely to metastasize

Question 18

METASTASIZE

Answer 18

cells can break away from the original mass and travel in the bloodstream or lymphatic system to colonize other areas of the body

Question 19

CANCER

Answer 19

a class of diseases characterized by malignant cells

Question 20

The mechanics of cancer

Answer 20

Cancer begins when a single cell accumulates genetic mutations that cause it to break through its death and division controls. As the cell continues to divide a tumor develops. All tumors grow slowly at at first because only a few cells are divine, but not all cells continue to grow at the same rate.

Question 21

How do cancer cells differ from normal cells

Answer 21

1. uncontrolled cell division (no connective tissue capsule)
2. they look different: rounder, cell membrane is more fluid, loses some specialized features from parent cells, may have multiple nuclei
3. they are immortal: they ignore the clock that limits normal cells to about 50 cell divisions: they have high telemorase
4. GROWTH FACTORS: cancer cells divide even in their absence
5. They lack CONTACT INHIBITION
6. They lack ANCHORAGE DEPENDENCE
   ( explains why metastasis occurs)
7. does not undergo apoptosis when badly damaged
8. They send signals to develop new blood vessels enabling a tumor to have its own blood supply

Question 22

Where does cellular clock reside

Answer 22

in TELOMERES

Question 23

what are TELOMERES

Answer 23

The encoding dan at the tips of eukaryotic chromosomes

Question 24

What do TELOMERES do

Answer 24

They consists of hundreds to thousands of repeats of a specific DNA sequence, at each cell division, the elopers loose nucleotides from their ends, so that the chromosomes become shorter. After about 50 divisions all that loss signals division to cease in a normal cell.

Question 25

TELOMERASE

Answer 25

cells that produce the enzyme telomerase can continually add dan to chromosome tips. their chromosomes stay long which enables them to divide beyond the approx 50 division limit

Question 26

GROWTH FACTORS

Answer 26

proteins that stimulate cell division

Question 27

e.g. of growth factor

Answer 27

epidermal growth factor stimulate cells to divide to produce new skin

Question 28

CONTACT INHIBITION

Answer 28

normal cells stop dividing when they touch on another in a one -cell thick layer in a culture

Question 29

ANCHORAGE DEPENDENCE

Answer 29

normal cells only divide when attached to a solid surface

Question 30

What macromolecule control the cell cycle and apoptosis

Answer 30

proteins. genes encode proteins

Question 31

What 2 classes of cancer- related genes play a role in the development of cancer.

Answer 31

1. oncogenes | 2. tumor supressor gene

Question 32

ONCOGENES ( onko, mass or lump)

Answer 32

Mutated variants of genes that normally stimulate cell division

Question 33

The normal versions of oncogenes are called

Answer 33

PROTO-ONCOGENES

Question 34

PROTO-ONCOGENES

Answer 34

encode many types of proteins If the protein is abnormally active or expressed at too high a concentration, the cell cycle will be accelerated, and cancer may develop

Question 35

why are oncogenes especially dangerous

Answer 35

because only one of the two versions in a cell (from dad and mom) needs to be damaged for cancer to develop. The oncogenes are

Question 36

The oncogene's protein

Answer 36

Is abnormal and is an accelerator that overrides the normal protein encoded by the proto-oncogene

Question 37

TUMOR SUPPRESSOR GENES

Answer 37

encode proteins that normally block cancer development: they promote apoptosis or prevent cell division. they block cancer from developing. . Unlike oncogenes both of the versions of this gene must be damaged for cancer to develop: as long as one tumor suppressor gene is functioning , the cell continues to produce protective proteins

Question 38

The more oncogenes or mutated tumor suppressor genes in a person's cell

Answer 38

the higher the probability of cancer

Question 39

How is the spread of cancer usually described

Answer 39

In stages

Question 40

Why are chemotherapy and radiation considered blunt tools to treat cancer

Answer 40

because they target all rapidly dividing cells whether cancerous or not

Question 41

egs of normally rapidly diving cells

Answer 41

bone marrow, digestive tract and hair follicles

Question 42

What prevents normal cells from dividing when they are not supposed to?

Answer 42

Interactions between signaling proteins produces checkpoints in the cell cycle to ensure that cells do not divide at improper times.

Question 43

What happens at cell cycle checkpoints

Answer 43

At cell cycle checkpoints, the cell cycle is controlled, ensuring that each stage of the cycle is completed before the next stage begins. A cell will only proceed into mitosis if the G1, S, and G2 checkpoints have been successfully passed. If they have not, the cell may stop or suspend the cell cycle, or may enter apoptosis and die.

Question 44

. What is the difference between a benign and a malignant tumor?

Answer 44

Benign tumors do not spread to other areas of the body and do not invade nearby tissues. A malignant tumor does invade nearby tissues and may metastasize to colonize other areas of the body.

Question 45

How do cancer cells differ from normal cells

Answer 45

Cancer cells are different from normal cells in that they have lost the normal controls on the cell cycle. Cancer cells therefore divide in an unregulated fashion. Cancer cells look different from normal cells and lose some of the special features of the parent cell. Cancer cells may have their own growth factors that signal when they should divide. Cancer cells lack contact inhibition; in addition, they are essentially immortal and lack apoptosis. Cancer cells can stimulate the growth of new blood vessels that supply them with nourishment and remove wastes.

Question 46

What is the relationship between mutations and cancer

Answer 46

Mutations cause changes to the signaling proteins that act as checkpoints on division or that signal apoptosis. These changes result in cells that continually divide and do not undergo cell death.

Question 47

How does a person acquire the mutations associated with cancer?

Answer 47

Mutations can be inherited or caused by exposure to mutagens such as UV radiation or tobacco chemicals. Some sexually transmitted viruses also cause cancer. Lifestyle choices such as eating right and exercising might help prevent mutations associated with cancer.

Question 48

Distinguish among the treatments for cancer

Answer 48

Surgical tumor removal is a direct and local treatment that removes just the cancerous mass and often nearby lymph nodes. Chemotherapy and radiation treatments are both “blunt” tools that target any rapidly dividing cell types, though radiation treatment is much more localized.