Author: Philip Colls
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Cell Cycle (Mitosis) booklet revision questions   NAME: 
Q1. A student investigated mitosis in the tissue from an onion root tip.
(a)     The student prepared a temporary mount of the onion tissue on a glass slide. She covered the tissue with a cover slip. She was then given the following instruction.
“Push down hard on the cover slip, but do not push the cover slip sideways.”
Explain why she was given this instruction.
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The image below shows one cell the student saw in the onion tissue.
 
© Ed Reschke/
Oxford Scientific/Getty Images
(b)     The student concluded that the cell in the image above was in the anaphase stage of mitosis. Was she correct? Give two reasons for your answer.
1. _________________________________________________________________
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2. _________________________________________________________________
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(c)     The student counted the number of cells she observed in each stage of mitosis.
Of the 200 cells she counted, only six were in anaphase.
One cell cycle of onion root tissue takes 16 hours. Calculate how many minutes these cells spend in anaphase.
Show your working.

 
Answer = ____________________ minutes                          (2)(Total 6 marks)
Q2.
(a)     The diagram shows a stage of mitosis in an animal cell.
 
(i)      Name this stage.
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(1)
(ii)     Describe what happens during this stage that results in the production of two genetically identical cells.
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(2)
(b)     A sample of epithelial tissue from the small intestine of an animal was analysed.
Some of the cells had 8.4 units of DNA, others had only 4.2 units.
(i)      Use your knowledge of the cell cycle to explain why some cells had 8.4 units of DNA and others had only 4.2 units.
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(2)
(ii)     How many units of DNA would you expect to be present in a gamete formed in this animal as a result of meiosis?
 
(1)
(Total 6 marks)
Q3.
The diagram shows a cell cycle.
 
(a)     The table shows the number of chromosomes and the mass of DNA in different nuclei.
All the nuclei come from the same animal. Complete this table.
 
Nucleus | Number of chromosomes | Mass of DNA / arbitrary units
At prophase of mitosis | 26 | 60
At telophase of mitosis | |
From a sperm cell | |
(4)
(b)     If the DNA of the cell is damaged, a protein called p53 stops the cell cycle.
Mutation in the gene for p53 could cause cancer to develop. Explain how.
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(3)
(c)     Drugs are used to treat cancer. At what phase in the cell cycle would each of the following drugs act?
(i)      A drug that prevents DNA replication
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(ii)     A drug that prevents spindle fibres shortening
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(Total 9 marks)
Q4.
The diagram shows a cell cycle.
 
(a)     In prophase of mitosis, the chromosomes become visible. Describe what happens in
(i)      metaphase
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(2)
(ii)     anaphase.
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(2)
(b)     (i)      Cells lining the human intestine complete the cell cycle in a short time. Explain the advantage of these cells completing the cell cycle in a short time.
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(1)
(ii)     The time required for a cell to complete the cell cycle was 4 hours 18 minutes.
Calculate the time required in minutes for this cell to multiply to produce eight cells.
Show your working.

 

Answer ____________________
(2)
(c)     Mikanolide is a drug that inhibits the enzyme DNA polymerase. Explain why this drug may be effective against some types of cancer.
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(2)
(Total 9 marks)
 
Q5.
(a)     Mitosis is important in the life of an organism. Give two reasons why.
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(2)
A biologist used a microscope to investigate plant tissue where some of the cells were dividing by mitosis. She examined 200 cells and counted the number of cells in interphase and in each stage of mitosis.
The table shows some of the cells she saw, and the percentage of cells in interphase and in two stages of mitosis, A and B.
 
Stage of cell cycle | Percentage of cells
Interphase | | 90
Stage A | | 3
Stage B | | 1
                                              Images by Edmund Beecher Wilson [Public domain], via Wikimedia Commons
(b)     (i)      Explain why the biologist chose to examine 200 cells.
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(1)

(ii)     Name Stage A and Stage B. Give the evidence from the photograph that you used to identify the stage.
Name of Stage A________________________________________________
Evidence ______________________________________________________
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Name of Stage B________________________________________________
Evidence ______________________________________________________
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(4)
(c)     In this tissue one complete cell cycle took 20 hours.
Using information from the table, calculate the mean time for these cells to complete mitosis. Show your working.

Answer ____________________
(2)
(Total 9 marks)
Q6.
Figure 1 shows all the chromosomes present in one human cell during mitosis. A scientist stained and photographed the chromosomes. In Figure 2, the scientist has arranged the images of these chromosomes in homologous pairs.
 
Figure 1 | Figure 2

(a)     Give two pieces of evidence from Figure 1 that this cell was undergoing mitosis. Explain your answers.
1. _________________________________________________________________
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2. _________________________________________________________________
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(b)     Tick (✓) one box that gives the name of the stage of mitosis shown in Figure 1.
 
A | Anaphase |
B | Interphase |
C | Prophase |
D | Telophase |
(1)
(c)     When preparing the cells for observation the scientist placed them in a solution that had a slightly higher (less negative) water potential than the cytoplasm. This did not cause the cells to burst but moved the chromosomes further apart in order to reduce the overlapping of the chromosomes when observed with an optical microscope.
Suggest how this procedure moved the chromosomes apart.
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(d)     The dark stain used on the chromosomes binds more to some areas of the chromosomes than others, giving the chromosomes a striped appearance.
Suggest one way the structure of the chromosome could differ along its length to result in the stain binding more in some areas.
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(e)     In Figure 2 the chromosomes are arranged in homologous pairs.
What is a homologous pair of chromosomes?
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(f)      Give two ways in which the arrangement of prokaryotic DNA is different from the arrangement of the human DNA in Figure 1.
1. _________________________________________________________________
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2. _________________________________________________________________
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_____________________________________________________(2)(Total 9 marks)
Q7. (a)     Describe and explain how the structure of DNA results in accurate replication.
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(b)     Describe the behaviour of chromosomes during mitosis and explain how this results in the production of two genetically identical cells.
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(c)     A cancerous tumour is formed by uncontrolled mitotic division. This results in a mass of cells with an inadequate blood supply. Drugs are being developed which only kill cells in a low oxygen environment. Suggest how these drugs could be useful in the treatment of cancer.
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____________________________________________________(2)(Total 13 marks)
Q8. (a)     A student prepared a stained squash of cells from the tip of an onion root and observed it using an optical microscope.
During the preparation of the slide, he:
•        cut the first 5 mm from the tip of an onion root and placed it on a glass slide
•        covered this tip with a drop of stain solution and a cover slip
•        warmed the glass slide
•        pressed down firmly on the cover slip.
He identified and counted nuclei in different stages of the cell cycle.
Explain why the student:
1. used only the first 5 mm from the tip of an onion root.
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2. pressed down firmly on the cover slip.
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(2)
Figure 1 shows the cells the student saw in one field of view. He used this field of view to calculate the length of time these onion cells spent in anaphase of mitosis.
Figure 1

(b)     Scientists have found the mean length of time spent by onion cells in anaphase of mitosis is 105 minutes. They also found the cell cycle of cells in the onion root shown in Figure 1 takes 1080 minutes.
32 whole cells are shown in Figure 1.
Use this information and Figure 1 to calculate the length of time the cells of this onion root are in anaphase and then calculate the percentage difference between your answer and the mean length of time found by the scientists.
Show your working.
Answer = ____________________ %
(2)
(c)     Tick (✓) the name given to the division of cytoplasm during the cell cycle.
 
A | Binary fission |
B | Cytokinesis |
C | Phagocytosis |
D | Segregation |
(1)
(d)     Describe and explain what the student should have done when counting cells to make sure that the mitotic index he obtained for this root tip was accurate.
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(e)     A scientist treated growing tips of onion roots with a chemical that stops roots growing. After 24 hours, he prepared a stained squash of these root tips.
Figure 2 is a drawing showing the chromosomes in a single cell observed in the squash of one of these root tips in anaphase. This cell was typical of other cells in anaphase in these root tips.
Figure 2

Use all of this information to suggest how the chemical stops the growth of roots.
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(3)
(Total 10 marks)

Q9. Scientists investigated the effect of bromelain on cancer cells. They took cells from skin cancers in mice and added them to a liquid growth medium in two dishes.
Four hours later they added a solution of bromelain to one of the dishes. They left the other dish as a control. They also added a substance to both dishes that is turned purple by respiring cells.
Both dishes were placed in an incubator. The scientists measured the intensity of the purple colour at intervals over a period of 100 hours.
 
(a)     The scientists put the same number of skin tumour cells in each dish at the start of this investigation. Explain why it was important to put the same number of cells in each dish.
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(b)     The scientists concluded that bromelain did not kill cancer cells but stopped them dividing. Does the graph support this conclusion? Explain your answer.
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(c)     An article in a newspaper claimed that these data show that bromelain can be used to treat cancer.
Give three reasons why we should be careful about accepting this claim.
1. _________________________________________________________________
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2. _________________________________________________________________
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3. _________________________________________________________________
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(3)
(d)     The rate of cell division is important in investigations into cancer. Suggest why.
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(2)
(e)     Scientists have investigated the effects of bromelain on cancer growth in humans. Suggest why they gave bromelain in addition to, rather than instead of, the usual treatment.
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(2)
(Total 10 marks)

Mark schemes
Q1.
(a)     1.      Push hard – spread / squash tissue;
2.      Not push sideways – avoid rolling cells together / breaking chromosomes.
Neutral – to see cells clearly
2
(b)     No (no mark)
Yes (no mark)
1.      Chromosomes / chromatids are (in two groups) at poles of spindle / at ends of spindle;
Do not accept ‘ends of cell’
2.      V-shape shows that (sister) chromatids have been pulled apart at their centromeres / that centromeres of (sister) chromatids have been pulled apart.
2
(c)     28.8 / 29.
If incorrect, allow:
 = 1 mark
2
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Q2.
(a)     (i)      Anaphase
1
(ii)     1.      Sister / identical chromatids / identical chromosomes;
Reject: Homologous chromosomes separate.
Allow any reference to chromatids / chromosomes being identical e.g. same DNA
2.      To (opposite) poles / ends / sides;
2
(b)     (i)      1.      8.4 / cells with twice DNA content = replicated DNA / late interphase / prophase / metaphase / anaphase;
Any reference to interphase must suggest towards end of interphase.
'Chromosomes replicate' is not enough for DNA replicates.
2.      4.2 = DNA not replicated / (early) interphase / telophase / cell just divided / finished mitosis;
2
(ii)     2.1;
1
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Q3.
(a)     
Nucleus | Number of chromosomes | Mass of DNA / arbitrary units
At telophase of mitosis | 26; | 30;
From a sperm cell | 13; | 15;
4
(b)     Cancer cells often have faulty / damaged DNA;
Protein / p53 faulty / not made;
Cell (with faulty / DNA) divides / completes cell cycle;
Uncontrolled division produces cancer;
p53 refers to the protein so do not accept reference to p53 mutating.
3
(c)     (i)      Interphase / S phase / synthesis phase;
1
(ii)     Anaphase / A;
1
[9]
Q4.
(a)     (i)      Spindle formed / chromosome / centromere / chromatids
attaches to spindle;
Chromosomes / chromatids line up / move to middle / equator
(of cell);
Do not award second mark for answers referring to chromosomes ‘pairing up’.
Ignore reference to homologous chromosomes unless context suggests pairing which negates second mark.
Neutral: Details on nuclear membrane.
Accept: Diagram for second marking point.
2
(ii)     Chromosome / centromere splits / chromatids / ‘chromosomes’ separate / pulled apart;
To (opposite) sides / poles / centrioles (of cell);
Reject: Homologous chromosomes separate for first marking point.
Accept: Diagram for second marking point.
Chromatids / ‘chromosomes’ move to poles / sides / centrioles = 2 marks.
2
(b)     (i)      Form / replace cells quickly / rapidly / divide / multiply / replicate rapidly;
Neutral: Repair cells.
Answers must convey idea of ‘speed’.
1
(Ii)     Correct answer = 774 minutes / 12 hours 54mins = 2 marks;;
Incorrect answer but indicates 3 cell cycles involved = one mark;
2
(c)     Prevents / slows DNA replication / doubling / prevents / slows mitosis;
New strand not formed / nucleotides (of new strand) not joined
together / sugar-phosphate bonds not formed;
First marking point must be in context of DNA replication not cell replication.
Do not negate first marking point if role of DNA polymerase is described incorrectly e.g. Reject: ‘joins bases / strands together’.
Role of DNA polymerase must be correct for last marking point.
2
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Q5.
(a)     1.      Growth / increase in cell number;
Ignore growth of cells
2.      Replace cells / repair tissue / organs / body;
Ignore repair cells
Reject bacteria
3.      Genetically identical cells;
‘Produces 2 genetically identical cells’ does not reach MP1 as well as MP3
4.      Asexual reproduction / cloning;
Allow example or description
2 max
(b)     (i)     (Ensures) representative (sample);
Accept find some cells in mitosis / not in interphase.
Accept ‘more reliable’ only if linked to percentage (of cells).‘Improves reliability’ on its own does not gain this mark
Neutral: Large sample
1
(ii)     1.      A = metaphase;
2.      Chromosome / chromatids lie on equator;
Reject homologous chromosomes Allow centre / middle
3.      B = anaphase;
4.      Chromatids / chromosomes separating / moving apart / moving to poles;
Reject homologous chromosomes
4
(c)     2 hours / 120 minutes;
Allow 1 mark if working shows candidate understood that mitosis would take 10%
2
[9]
Q6.
(a)     1.      The (individual) chromosomes are visible because they have condensed;
Both parts of each answer are required – evidence and explanation.
For ‘they’ accept ‘chromosomes/chromatin/DNA’
Accept ‘tightly coiled’ or ‘short and thick’ for condensed but do not accept ‘contracted’.
Ignore references to nucleus/nucleolus/nuclear membrane.
2.      (Each) chromosome is made up of two chromatids because DNA has replicated;
Both parts of each answer are required – evidence and explanation.
Accept ‘sister chromatids’ for ‘two chromatids’.
Ignore references to nucleus/nucleolus/nuclear membrane.
3.      The chromosomes are not arranged in homologous pairs, which they would be if it was meiosis;
Both parts of each answer are required – evidence and explanation.
Accept not meiosis because bivalents/chiasmata/crossing over not seen.
Ignore references to nucleus/nucleolus/nuclear membrane.
2 max
(b)     Automarked q – ✔ prophase
1
(c)     1.      Water moves into the cells/cytoplasm by osmosis;
Reject water moving into chromosomes/nucleus.
2.      Cell/cytoplasm gets bigger;
Accept idea of cell/cytoplasm has greater volume/swells/expands.
Ignore references to pressure changes, turgidity and chromosomes being more dilute.
Ignore references to changing water/fluid contents of the cell.
Allow ECF for ‘nucleus expands’ but not for ‘chromosomes expand’.
2
(d)     Differences in base sequences
OR
Differences in histones/interaction with histones
OR
Differences in condensation/(super)coiling;
Answer must be in context of differences in arrangement of chromosomes not just related to the properties of the stain.
Accept spec section 8 ideas e.g. different methylation/acetylation
Accept different genes
Reject different alleles
1
(e)     (Two chromosomes that) carry the same genes;
Reject ‘same alleles’
Accept ‘same loci’ (plural) or ‘genes for the same characteristics’
1
(f)      (Prokaryotic DNA) is
1.      Circular (as opposed to linear);
2.      Not associated with proteins/histones ;
3.      Only one molecule/piece of DNA
OR
present as plasmids;
Max 1 if prokaryotic DNA only found as plasmids OR if prokaryotic DNA is single stranded.
Ignore references to nucleus, exons, introns or length of DNA. Do not credit converse statements.
Ignore descriptions of eukaryotic DNA alone.
2 max
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Q7.
(a)     1       two strands therefore semi-conservative replication (possible);
2       base pairing / hydrogen bonds holds strands together
3       hydrogen bonds weak / easily broken, allow strands to separate;
4       bases (sequence) (exposed so) act as template / can be copied;
5       A with T, C with G / complementary copy;
6       DNA one parent and one new strand; 
4 max
(b)     1       chromosomes shorten / thicken / supercoiling;
2       chromosomes (each) two identical chromatids / strands / copies 
(due to replication);
3       chromosomes / chromatids move to equator / middle of the spindle / cell;
4       attach to individual spindle fibres;
5       spindle fibres contract / centromeres divide / repel;
6       (sister) chromatids / chromosomes (separate) 
move to opposite poles / ends of the spindle;
7       each pole / end receives all genetic information / 
identical copies of each chromosome;
8       nuclear envelope forms around each group of chromosomes / 
chromatids / at each pole;
7 max
(c)     cancer cells killed, normal body cells survive;
cancer cells low oxygen (as blood supply cannot satisfy demand);
2
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Q8.
(a)     1.      Where dividing cells are found / mitosis occurs;
OR
No dividing cells / mitosis in tissue further away / more than 5 mm from tip;
OR
To get (soft) tissue that will squash;
OR
Length that will fit under cover slip;
Accept most dividing cells
2.      Single / thin layer of cells / spread out cells so light passes through (making cells / nuclei visible);
Accept thin layer of tissue
Ignore to see cells clearly
2
(b)     3.57 / 3.6 / 3.7 / 3.71 / 3.8 (%);;
If the answer includes additional decimal places, award the marks if it would round to a correct answer
There are 3 cells in anaphase
Accept for 1 mark, 101.25 / 101 (students estimate in minutes)
OR
3.75 (difference between scientist estimate and student’s estimate in minutes)
Ignore plus or minus signs
2
(c)     Cytokinesis;
1
(d)     Description;
Explanation;
E.g,
1.      Examine large number of fields of view / many cells;
Mark as pairs only
Accept large number / 20 or more for many
2.      To ensure representative sample;
Accept typical / reliable
OR
3.      Repeat count;
4.      To ensure figures are correct;
OR
5.      Method to deal with part cells shown at edge /count only whole cells;
6.      To standardise counting;
2 max
(e)     1.      Stops anaphase / cell division / mitosis;
Accept prevents telophase / cytokinesis
2.      (By) stopping / disrupting / spindle fibres forming / attaching / pulling;
Ignore affects anaphase
3.      Preventing separation of (sister) chromatids;
Ignore chromosomes separate / split
Accept chromatids split
4.      (So) no new cells added (to root tip);
3 max
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Q9.
(a)     To ensure the colour is the same at the start;
1
(b)     Yes – curve on graph with bromelain present remains approximately constant / rises very slightly;
Would decrease if killing of cells occurred / would increase if cells still dividing;
2
(c)     Use of mouse cells (rather than human);
(Carried out) in vitro / not in living organisms;
Only tested on one type of cancer;
Not possible to predict effect on humans (as no data collected);
3 max
(d)     The faster the rate of division the faster the cancer would grow;
By measuring rate of cell division you could see how effective the treatment was;
2
(c)     Not ethical to replace conventional treatment;
As life of patient is at risk (if bromelain not effective);
2
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