Mitosis and The Cell Cycle Flashcards
(22 cards)
Calculate the rate of movement of the centromeres during phase E.
Give your answer in μm minute–1 and to 3 decimal places.
1.286
Name the three phases of mitosis shown by C, D and E on the figure above.
Describe the role of the spindle fibres and the behaviour of the chromosomes during each
of these phases.
prophase
metaphase
anaphase
Role: Attach to centromere
in prophase chromosomes condense and become visible
in metaphase chromosomes line on the equator
CENTROMERES ATTACH TO SPINDLE FIBRES
in anaphase chromatids are pulled to each opposite poles
Describe and explain the arrangement of the genetic material shown in the above image
Chromosomes are becoming visible because they are still condensing
Name the fixed position occupied by a gene on a DNA molecule
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
because nucleotide/base sequence
in triplets
have a specific amino acid sequence / primary structure
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.
4.7
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.
TREXELL acts as a competitive inhibitor
Trexall competes with substrate/Folic acid and is able to bind to active site
Less enzyme substrate complexes formed
Fewer/not enough nucleotides available for 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
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.
The formula for the volume of a sphere is where π = 3.14
32015
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)
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’
In some cases (with 30 mg) there was a 100% reduction in size/tumours would
have been eradicated;
Against (the use of 30 mg)
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
(No idea of) extra cost of providing 30 mg per week;
(Increased risk of) side effects with higher doses;
Apart from age and general health, give two important factors when choosing patients for
this investigation.
body mass
ethnicity
A student analysed the table above and concluded that Trexall was effective in reducing
pain in arthritis patients.
Evaluate the student’s conclusion.
FOR
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
Small sample size/only 12 people/only studied females / effects in males could
be different;
(Mean score for severity of) pain in control group/Group S is (also) lower;
No statistical testing, so do not know if decrease/difference is significant;
Ignore ‘do not know if results are significant’
Pain is (a) subjective (measurement);
Accept ‘patients might lie about pain
Mitosis is important in the life of an organism. Give two reasons why.
growth
repairing tissue
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.
2 hrs
In which phase of the cell cycle does DNA replication take place?
interphase
Describe the role of the spindle during mitosis.
attach to centromere
separation of chromosomes/chromatids
Meiosis also occurs during the life cycle of organisms. What is the importance of meiosis?
variation
halfing number of chromosomes
Explain the change in the DNA content during stage S
nucleus is dividing
Suggest why the student soaked the root tips in hydrochloric acid in step 2.
to squash the root
so the stain can diffuse in
Pressing the coverslip downwards enabled the student to observe the stages of mitosis
clearly.
Explain why.
To create a single/thin layer of cells
OR
To spread out cells;
So that light could pass through;
Other students in the class followed the same method, but calculated different mitotic
indices.
Apart from student errors, suggest two explanations why.
Different fields of view are different samples
Garlic grown for different lengths of time
