Cell Cycles

Question 1

Do all multicellular organisms divide continuously?

Answer 1

Only some cells in multicellular organisms retain the ability to divide.

Question 2

What type of cells undergo a normal cell cycle that is separated by periods of cell growth?

Answer 2

Cells that do not divide continuously in multicellular organisms.

Question 3

How many stages does the cell cycle have?

Answer 3

3

Question 4

What are the three stages of the cell cycle?

Answer 4

Interphase
Nuclear division
Division of the cytoplasm (cytokinesis)

Question 5

How much of the cell cycle does interphase take up?

Answer 5

This occupies most of the cell cycle and it sometimes seen as the resting phase.

Question 6

What happens during interphase?

Answer 6

No division takes place.

Question 7

What happens in nuclear division?

Answer 7

The nucleus divides either into either two (mitosis) or four (meiosis).

Question 8

What happens in cytokinesis?

Answer 8

This is where cytoplasm divides to produce two new cells (mitosis) or four new cells (meiosis).

Question 9

What follows nuclear division?

Answer 9

Cytokinesis.

Question 10

Are all cell cycles the same length?

Answer 10

No, the length of a complete cell cycle varies greatly amongst organisms.

Question 11

How much time do mammalian cells tend to spend in interphase?

Answer 11

About 90%

Question 12

What is the typical length of the mammalian cell cycle?

Answer 12

24 hours

Question 13

What is cancer caused by?

Answer 13

A growth disorder of cells.

Question 14

What does the growth disorder of cells lead to?

Answer 14

This leads to uncontrolled growth and division cells to create a tumour.

Question 15

What does the tumour do?

Answer 15

It constantly grows in size.

Question 16

Where can tumours develop?

Answer 16

They can develop in any organ in the body.

Question 17

When does the tumour become cancerous?

Answer 17

It becomes cancerous if it changes from benign to malignant.

Question 18

What is the rate of mitosis controlled by?

Answer 18

It is controlled by the environment of the cell and by growth factors. It is also controlled by two types of gene.

Question 19

What results in uncontrolled mitosis?

Answer 19

A mutation in one of the two types of gene that controls growth.

Question 20

How are mutant cells different from normal cells?

Answer 20

Mutant cells are usually structurally and functionally different from normal cells.

Question 21

True or false: all mutant cells survive?

Answer 21

This is false, most mutated cells die however, any that survive are capable of dividing to form clones of themselves and form tumours.

Question 22

What are the key features of malignant tumours?

Answer 22

They grow rapidly, they are less compact and they are more likely to be life-threatening.

Question 23

What are the key features of benign tumours?

Answer 23

Benign tumours grow more slowly, are more compact and are less likely to be life-threatening.

Question 24

What does the treatment of cancer often involve?

Answer 24

It often involves killing dividing cells by blocking a part of the cell cycle, this disrupts the cell division and therefore stops cancer growth.

Question 25

How do drugs used to treat cancer usually disrupt the cell cycle?

Answer 25

They prevent DNA from replicating.

They inhibit the metaphase stage of mitosis by interfering with the spindle formation.

Question 26

How do cancer drugs inhibit the metaphase stage of mitosis?

Answer 26

They interfere with the formation of spindle fibres.

Question 27

What is the main problem with chemotherapy?

Answer 27

It also disrupts the cell cycle of normal cells.

Question 28

What type of cells are cancer drugs more effective at stopping growth?

Answer 28

They are more effective against rapidly dividing cells. As cancer cells have a particularly fast rate of division, they are damaged to a greater degree than normal cells. Those normal cells such as hair-producing cells are also vulnerable to damage because they divide rapidly.