3.2.2 - Mitosis and Cell Cycle

Question 1

What are the 4 stages of mitosis?

Answer 1

Prophase

Metaphase

Anaphase

Telophase (cytokinesis)

Question 2

What does the diagram show?

Answer 2

Anaphase

Question 3

Cancer is caused by uncontrolled mitosis. How do most cancer drugs work?

Answer 3

1. Preventing DNA replication/
2. Inhibiting metaphase stage of mitosis by interfering with spindle formation.

Question 4

What happens during prophase?

Answer 4

• DNA condenses into chromosomes (becomes visible)
• Centrioles move to opposite poles of cell and spindle fibres are released to form a spindle apparatus.
• The nucleolus and nuclear envelope break down.

Question 5

What does the diagram show?

Answer 5

Telophase (leading to cytokinesis)

Question 6

Describe the process of bacterial binary fission

Answer 6

• Circular DNA and plasmids replicate.
• The cell membrane begins to grow and pinches in around the two circular DNA molecules.
• A new cell wall forms between the two circular DNA molecules dividing the cell into 2 idenitcal daughter cells.
• The cells have variable numbers of plasmids.

Question 7

What does the diagram show?

Answer 7

Metaphase

Question 8

When would mitosis not result in 2 identical daughter cells?

Answer 8

If there was a mutation (very rare)

Question 9

Gametes (eggs and sperm) are haploid cells. What is meant by this?

Answer 9

They contain only 1 set of unparied chromosomes.

Question 10

What is mitosis important for?

Answer 10

• Growth
• Repair of damaged cells.
• Reproduction (single celled organisms)

Question 11

Describe what happens when a virus replicates.

Answer 11

• Attachment to host cell using attachment proteins on their surface.
• Injection of nucleic acid into host cell.
• Nucleic acid provides instructions for host cell’s metabolic machinary to start producing new viral components e.g. enzymes and structural proteins.
• Viral components packaged into new viruses.

Question 12

What happens during metaphase?

Answer 12

Chromosomes are positioned along equator of cell by spindle fibres.

Question 13

What is the product of mitosis?

Answer 13

2 daughter cells that have the same number of chromosomes as the parent cell and each other.

Question 14

What does the diagram show?

Answer 14

Prophase

Question 15

The regular cycle of division separated by periods of cell growth is called…

Answer 15

the cell cycle

Question 16

How much of a single cell cycle is spent in interphase?

Answer 16

approximately 90%

Question 17

Bacterial cells replicate in a similar way to mitosis. What do we call their method of replication?

Answer 17

Binary Fission

Question 18

The rate of mitosis is controlled by…

Answer 18

1. The environment of the cell
2. ‘Growth factors’.
3. Two genes.

Question 19

What happens during telophase?

Answer 19

• Chromatids reach opposite poles.
• Nucleas envelope and nucleolus reforms around chromosomes.
• Spindle apparatus disintegrates.
• Cytoplasm divides to complete cell division (cytokinesis).

Question 20

What are the 3 stages of the cell cycle?

Answer 20

Interphase

Nuclear division

Division of cyctoplasm (cytokinesis)

Question 21

How can we remember the order of the stages of mitosis?

Answer 21

• Prophase - (Preparation - condensing and spindle formation)
• Metaphase - (Middle - chromosomes lined up along middle of cell)
• Anaphase - (Action - chromatids pulled apart)
• Telophase - (Two - two new cells after division)

Question 22

How long does a mammalian cell to undergo 1 complete cell cycle?

Answer 22

24 hours

Question 23

What happens during anaphase?

Answer 23

• Spindle fibres contract to pull sister chromatids apart at the centromere.
• Chromatids move towards opposite poles.

Question 24

When a chromosome (DNA) replicates, the new stand is initially joined to the old at a place called the…

Answer 24

centromere.

Question 25

What are the advantages of reproducing via mitosis?

Answer 25

Only 1 parent required. Beneficial qualities are more likely to be passed on to offspring.

Question 26

A zygote is a **_diploid_** cell. What is meant by this?

Answer 26

A cell containing 2 complete sets of chromosomes (one from each parent)

Question 27

What are the disadvantages of reproducing by mitosis?

Answer 27

Less variation in offspring. Reduced ability to adapt to changing environment.

Question 28

What does the diagram show?

Answer 28

Interphase

Question 29

Describe a cell that is in **_interphase_**

Answer 29

Cell is actively synthesising proteins DNA replication Chromosomes are invisible

Question 30

why do you take cells from the root tip when studying mitosis?

Answer 30

Region where mitosis/cell division occurs;

Question 31

When when studying mitosis do you firmly squash the root tip?

Answer 31

To allow light through / make tissue layer thin;

Question 32

A cell under goes mitosis, the first division takes 24 hours and each subsequent one takes 8hours, how many cells are there after 3 days?

Answer 32

128

Question 33

How can you tell a cell has just under gone DNA replication?

Answer 33

Chromosomes are visiable as X shaped structures - 2 sister chromatids joined by a centromere

Question 34

During a root tip experiment why do we use the first 5mm of the root tip?

Answer 34

where the cells are under going mitosis

Question 35

during a root tip experiment why do we press firmly down on the cover slip?

Answer 35

make it single layer of cells SO light can pass through

Question 36

when counting cells during a root tip experiment - how can we be sure the mitotic index we calculate is accurate?

Answer 36

Look at many cells to ensure it is representative

Question 37

when growing bacteria, equipment must be sterile before use - suggest a way of sterilising equipment and why this is important?

Answer 37

boil in water/autoclave/wash in disinfectant to kill bateria thay may contaminate