Mitosis Exam Questions Flashcards
(19 cards)
0The diploid number of chromosomes in the body cell of an insect species is four.
Tick (✓) the box next to the diagram A, B, C or D that represents the appearance of
chromosomes in a cell during metaphase in this species.
A
Name the fixed position occupied by a gene on a DNA molecule.
Locus/Loci
Describe how a gene is a code for the production of a polypeptide. Do not include
information about transcription or translation in your answer
The DNA/nucleotide in triplets
determine order of amino acids sequence/primary structure of polypeptide
Use Figure 1 to calculate the percentage of maximum growth this type of tumour reaches
before it can be detected.
You will need to use the 10x
button on your calculator.
0.1
Figure 1 can also be used to calculate the age of this type of tumour.
At diagnosis, a patient had a tumour of 3.98 × 1011 cells.
Calculate the age of the tumour.
You will need to use the log10 button on your calculator.
4.8
Trexall is a drug that can be used to slow the development of various forms of cancer.
Trexall slows cell division by interacting with an enzyme called dihydrofolate reductase (DR).
DR is involved in making nucleotides; the substrate for DR is folic acid.
Figure 2 shows the chemical structure of Trexall.
Figure 3 shows the chemical structure of folic acid.
Use the information provided to suggest how Trexall slows cell division.
Trexall acts as a competitive inhibitor which binds to active site
Fewer enzyme substrate complexes formed
So fewer DNA nucleotides in DNA replication
The scientists measured the percentage change in tumour volume.
Suggest why they recorded both percentage change and tumour volume.
Percentage change
To allow comparison as tumours may differ in volume/size (at the start of the
investigation);
Tumour volume
(As) tumours may differ in length/width/shape
A lung cancer patient received 15 mg of Trexall per week. After treatment, the diameter of
his lung tumour was 35.8 mm
Assuming the tumour was spherical, use the mean percentage change in tumour volume
shown in Figure 4 to calculate the volume of the patient’s tumour before treatment with
Trexall.
32 015.93682
To reduce the size of tumours, would it be better to use 30 mg of Trexall per week, or 20 mg
of Trexall per week?
Explain your answer.
For (the use of 30 mg)
1. There is a significantly greater reduction (in tumour size with 30 mg), as SD
(bars) do not overlap;
Accept ‘significant difference’ for ‘significantly greater reduction’
2. In some cases (with 30 mg) there was a 100% reduction in size/tumours would
have been eradicated;
Against (the use of 30 mg)
3. There is too much/a lot of variation in effectiveness with 30 mg (in contrast with
20 mg);
Ignore 30 mg has a lot of deviation/large standard deviation’ unqualified
4. (No idea of) extra cost of providing 30 mg per week;
5. (Increased risk of) side effects with higher doses;
Apart from age and general health, give two important factors when choosing patients for
this investigation.
ethnicity
body mass
A student analysed the table above and concluded that Trexall was effective in reducing
pain in arthritis patients.
Evaluate the student’s conclusion.
For
1. Pain decreases more with Trexall/Group R compared with the control
group/Group S
OR
Pain decreases by 4.6 with Trexall/Group R and by 2 with the control
group/Group S;
Ignore numbers stated from the table, eg 9.7 to 5.1 and 9.8 to 7.8
Against
2. Small sample size/only 12 people/only studied females / effects in males could
be different;
3. (Mean score for severity of) pain in control group/Group S is (also) lower;
Could be subsumed within MP1
4. No statistical testing, so do not know if decrease/difference is significant;
Ignore ‘do not know if results are significant’
5. Pain is (a) subjective (measurement);
Mitosis is important in the life of an organism. Give two reasons why.
growth
repairing tissues
Explain why the biologist chose to examine 200 cells.
more representative sample
In which phase of the cell cycle does DNA replication take place?
interphase
Describe the role of the spindle during mitosis.
attach to centromere
Meiosis also occurs during the life cycle of organisms. What is the importance of meiosis?
variation
halving the number of chromosomes
Suggest why the student soaked the root tips in hydrochloric acid in step 2.
to squash the cell
so the stain can diffuse in
Pressing the coverslip downwards enabled the student to observe the stages of mitosis
clearly.
Explain why
to obtain a thin layer of root/cell
so light can be passed through easier when viewing under a microscope
Other students in the class followed the same method, but calculated different mitotic
indices.
Apart from student errors, suggest two explanations why.
different field of view of the sample
garlic grown different length
