mitosis Flashcards

Question 1

Q

Scientists investigated the effect of different concentrations of a kinesin inhibitor (KI) on mitosis of human bone-cancer cells grown in a culture.

The following table shows the scientists’ results.

Concentration of kinesin
inhibitor / nmol dm−3

Percentage of dividing human bone-cancer cells showing a monopolar mitotic spindle

0

1

0

10

8

100

93

1000

100

10 000

100

A student who saw these results concluded that in any future trials of this kinesin inhibitor with people, a concentration of 100 nmol dm−3 would be most appropriate to use.

Do these data support the student’s conclusion? Give reasons for your answer.

Answer

A

No, because) at 100 there are still some (7%) cancer cells dividing/undergoing mitosis;

Accept idea that all division stops only at 1000

So, cancer not destroyed/may continue to grow/spread/form tumours;

Must refer to cancer spreading not cells dividing

Best concentration may be between 100 and 1000/need trials between 100 and 1000;
This research in culture, don’t know effect of KI on people;

Reject ‘not tested on humans’

Reject ‘done in animals’

(Yes, because) above 100 produces little increase in % of cells not dividing/undergoing mitosis/at 100, most (93%) cancer cells unable to divide/dead;

Must clearly link lack of monopolar mitotic spindles with cell division

Above 100 may be harmful (to body);

Accept ‘above 100/high concentrations produce harmful side effects/named effects’

Higher concentrations more expensive;
(Above 100) will have more effect on (rapidly dividing) cancer cells;

Question 2

Q

Scientists looking for treatments for cancer are investigating the use of substances called kinesin inhibitors (KI). These inhibitors prevent successful mitosis. Some kinesin inhibitors cause the development of a monopolar spindle in mitosis.

The diagram below shows chromosomes attached to a normal mitotic spindle and to a monopolar mitotic spindle.

Suggest why the development of a monopolar mitotic spindle would prevent successful mitosis.

Answer

A

No separation of chromatids/chromosomes/centromeres;

Accept anaphase prevented

Accept nondisjunction

Reject homologous pairs

Chromatids/chromosomes all go to one pole/end/sides of cell/not pulled to opposite poles;
Doubles chromosome number in cell/one daughter cell gets no chromosomes or chromatids;

Question 3

Q

Explain how the doctor could have recognised which cells were in interphase when looking at the tissue samples

Answer

A

No visible chromosomes / chromatids / visible nucleus;

Question 4

Q

Banana growers can only grow new variety B plants from suckers. Suckers grow from cells at the base of the stem of the parent plant.

Use your knowledge of cell division to explain how growing variety B on a large scale will affect the genetic diversity of bananas.

Answer

A

Low genetic diversity because they are produced by mitosis;

Will all have the same DNA / genes / alleles / will be genetically identical / will be clones;

Question 5

Q

Most plants produce seeds after fertilisation in sexual reproduction. However, dandelions produce small, windblown seeds without fertilisation taking place. Suggest two advantages to the dandelion of being able to reproduce from these seeds, as well as from pieces of root.

Advantage 1 ________________________________________________________

___________________________________________________________________

Advantage 2 __

Answer

A

(different)
environmental conditions / named environmental factor / mutation;

1

(c) dispersal / prevent overcrowding / competition / colonise ;

increased number of (proven) offspring

Question 6

Q

anaphase Describe and explain what happens during this stage which ensures that two genetically identical cells are produced.

Answer

A

sister / identical chromatids (separate);

move to opposite poles / ends / sides;

Question 7

Q

In interphase Apart from an increase in the amount of DNA, give one process which occurs during stage X which enables nuclear division to occur.

Answer

A

ATP production / protein synthesis / replication of centrioles;

Question 8

Q

The table shows the average duration of each stage of the cell cycle in the cells of a mammalian embryo.

Stage

Mean duration/
minutes

Interphase

12

Prophase

50

Metaphase

15

Anaphase

10

Telophase

42

Give one piece of evidence from the table which indicates that these cells are multiplying rapidly.

Answer

A

short duration of interphase;

Question 9

Q

Read the following passage.

In laboratory tests, scientists investigated the effects of a new drug called ABZ

on stomach tumour cells. They found ABZ stopped mitosis by preventing the

formation of spindle fibres. They also found that ABZ affected some healthy

cells.

Mitosis is a controlled process. Cyclin B is a protein found in a cell’s nucleus. 5

It regulates the timing of mitosis during the cell cycle. Mitosis starts when the

concentration of Cyclin B in the nucleus rises sharply and ends when it falls.

The scientists found that ABZ increased, and maintained, a high concentration

of Cyclin B in stomach tumour cells.

Programmed cell death is called apoptosis. Two nuclear proteins, Bcl-2 and 10

Bax, are involved in controlling apoptosis. Apoptosis is prevented when the

ratio of Bcl-2 to Bax is high and is promoted when this ratio is low. The

scientists found that ABZ decreased the concentration of Bcl-2 and increased

the concentration of Bax in stomach tumour cells.

From their results the scientists claimed that ABZ could be used for the 15

successful treatment of stomach cancer.

Use information from the passage and your own understanding to answer the

questions.

(a) Suggest why preventing the formation of spindle fibres (lines 2–3) stopped the cell cycle.

___________________________________________________________________

(2)

(b) Suggest and explain why ABZ could be used as a treatment for cancer even though it affects some healthy cells (lines 3–4).

___________________________________________________________________

(1)

(c) What can you conclude about the effect of ABZ on tumour cells?

Use information about changes in the concentrations of Cyclin B (lines 6–7), and Bcl-2 and Bax (lines 10–14).

___________________________________________________________________

(4)

(d) Evaluate the scientists’ suggestion that ABZ could be used for the successful treatment of stomach cancer.

______________________________________________________________

Answer

A

Chromosomes/centromeres cannot attach (to spindle)

OR

Chromosomes cannot line up (on spindle);

2. (So, no) metaphase;

OR

3. Chromatids cannot separate (on spindle);

Accept description of ‘cannot separate’ e.g cannot move to poles

Ignore ‘split’

4. (So, no) anaphase;

2

(b) 1. Cancer cells divide more/uncontrollably/rapidly

OR

Healthy cells divide less/slowly;

1

(c)

Ignore references to spindle fibres

1. (ABZ) increases/maintains Cyclin B;

2. (So) mitosis (starts but) does not end (no tumour growth);

Ignore mitosis will continue

Ignore mitosis stops without qualification.

3. (ABZ) lowers ratio of Bcl-2 to Bax;

Accept (ABZ) decreases Bcl-2 and increases Bax

4. (So) apoptosis occurs/cells die (no tumour growth);

4

(d) In support of suggestion

1. Stops mitosis (at metaphase/anaphase)/cell division (so no tumour growth)

OR

Promotes apoptosis/programmed cell death (so tumour destroyed);

Against suggestion

2. Healthy cells (are) damaged/affected

OR

Causes side effects;

3. Results from laboratory tests/tests on (isolated) cells

OR

No clinical trials/tests on patients/people;

4. Dosage unknown;

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mitosis Flashcards

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