Mitosis

Question 0

Define cytokinesis.

Answer 0

The division of cytoplasm between two cells.

Question 1

Define mitosis.

Answer 1

Nuclear division where duplicated DNA divides into two daughter nuclei.

Question 2

What are chromosomes composed of?

Answer 2

DNA and histones.

Question 3

Define sister chromatids.

Answer 3

Two attached copies of a duplicated chromosome.

Question 4

Define daughter cells.

Answer 4

Produced by division from parent cells.

Question 5

Define homologous chromosomes.

Answer 5

A chromosome pair that have the same genes at the same loci.

Question 6

State the five features of interphase in mitosis.

Answer 6

1. The period when the cell isn’t dividing.
2. G1, S and G2.
3. Is more than 90% of the cell cycle.
4. Cell metabolic activity is high.
5. DNA is as loose as chromatin.

Question 7

State two features of the G0 stage.

Answer 7

1. Quiescent state between G1 and S.

2. Muscle and nerve cells stay in G0.

Question 8

State three features of the G1 phase.

Answer 8

1. It’s the primary growth phase.
2. It’s the longest stage in cell cycle.
3. There is an increase in size and complexity.

Question 9

State three features of the S phase.

Answer 9

1. It’s the synthesis stage.
2. The nuclear genome replicated.
3. One chromosome of two identical sister chromatids.

Question 10

State the five stages of the G2 phase.

Answer 10

1. It’s the second growth phase which prepared for genome separation.
2. Chromosomes start to condense.
3. Centriole pairs replicate.
4. Extensive tubulin production.
5. Microtubules assemble.

Question 11

State the two stages of M phase.

Answer 11

1. Mitosis - Nuclear division.

2. Cytokinesis - Cytoplasm divides then two daughter cells form.

Question 12

State two purposes of cyclins.

Answer 12

1. Two natural stop points exist at G1/S and G2/M. Cells do not pass these in the absence of positive “go ahead signals”.
2. In animals the cell cycle is driven by cytoplasmic proteins called cyclin-dependent kinases (CDKs). These are stable in amount but are activated by cyclins.

Question 13

What two things must occur before a cell divides?

Answer 13

1. A cell shouldn’t divide until it has accumulated enough cytoplasmic organelles to do so.
2. A cell must not start dividing until all its DNA has replicated. Failure to do so will result in damage to chromosomes.

Question 14

Define cyclins.

Answer 14

Proteins that appear and disappear rapidly with phases of the cell cycle.

Question 15

State three different types of microtubules that are involved in mitosis and their purpose.

Answer 15

1. Interpolar microtubules - Motor proteins associate with these and consequently drive spindle assembly.
2. Astral microtubules - They anchor the spindle pole.
3. Kinetochore microtubules - They pull sister chromatids apart.

Question 16

What are the five stages of mitosis?

Answer 16

1. Prophase.
2. Prometaphase.
3. Metaphase.
4. Anaphase.
5. Telophase.

Question 17

State the five stages of prophase in mitosis.

Answer 17

1. Chromatin keeps condensing.
2. Each chromosome appears as two sister chromatids.
3. Nucleoli disappear.
4. Microtubule extension starts moving centrosomes to opposite poles.
5. Mitotic spindle begins to form.

Question 18

State the six stages of prometaphase in mitosis.

Answer 18

1. Nuclear envelope fragments.
2. Microtubules extend through nuclear area.
3. Centrosomes approach poles.
4. Kinetochores attach chromatids to microtubules from opposite poles.
5. Pulling apart begins.
6. Interpolar microtubules extend past equator.

Question 19

State the three stages of metaphase in mitosis.

Answer 19

1. Centromeres are at opposite poles.
2. Chromosomes line up on metaphase plate.
3. Centromeres are on the plate, one chromatid on each side.

Question 20

State the six stages of anaphase in mitosis.

Answer 20

1. Cohesin (protein binding chromatids) is cleaved.
2. Each chromatid is one complete chromosome.
3. Microtubules shorten through tubulin being lost from the kinetochore end.
4. The chromosomes move to poles.
5. At the end of anaphase, each pole has a set of chromosomes.
6. Interpolar microtubules elongate cell.

Question 21

State the six stages of telophase in mitosis.

Answer 21

1. The interpolar microtubules elongate cell.
2. The spindle disassembles.
3. Two daughter nuclei form from envelope fragments.
4. Chromosomes get less condensed.
5. Nucleoli reappear.
6. Mitosis is complete and cytokinesis is underway.

Question 22

Describe how cytokinesis occurs in animal cells.

Answer 22

A cleavage furrow forms which bisects the cell, resulting in two daughter cells.

Question 23

Define cleavage furrow.

Answer 23

A contractile ring of actin and myosin filaments.

Question 24

Describe how cytokinesis occurs in plant cells.

Answer 24

A cell plate forms.

Question 25

Define cell plate.

Answer 25

A membrane of fused Golgi vesicles.

Question 26

What are three purposes of cell division?

Answer 26

1. It produces new single-called organisms.
2. It renews and repairs the multi-cellular body.
3. It produces new multicellular organisms from zygotes.

Question 27

What two cues are vital to regulation of mitosis?

Answer 27

1. Chemical cues (growth factors).

2. Physical cues (cell contact).

Question 28

Explain four reasons how cancer occurs.

Answer 28

1. Cancer cells don’t respond to ‘stop’ signals.
2. They divide excessively and can invade other tissues.
3. Division continues indefinitely.
4. Cells need to accumulate more than one mutation before they become cancerous.

Question 29

What two types of genes can influence the development of cancer?

Answer 29

1. Proto-oncogenes are involved in the normal stimulation of cell division. Mutation may cause them to become unregulated oncogenes.
2. Tumour suppressor genes may lose their functionality by mutation.