Topic 3 and 4 Exam Questions

Practicals:
5. Prepare and stain a root tip squash to observe the stages of mitosis
6. Identify sclerenchyma fibres, phloem sieve tubes and xylem vessels and their location within stems through a light microscope

Q1.
 
Cell division can be affected by various chemicals. The effects of these chemicals can be studied by observing tissues.
Herbicides are chemicals used to kill weeds. Some herbicides work by disrupting the cell cycle.
An investigation was carried out to study the effect of different concentrations of the herbicide Agil on mitosis in onion root tips.
The roots of onions were exposed to different concentrations of Agil for 24 hours.
Root tip squashes were then prepared and the mean mitotic index was calculated for each Agil concentration.
The results are shown in the table.

(i)  Describe the effects of Agil concentration on mitosis in onion root tips.
(2)
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(ii)  Devise an investigation to determine the effect of exposure time to Agil on the rate of mitosis in onion root tips.
(6)
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(Total for question = 8 marks)

Q2.
 
Answer the question with a cross in the box you think is correct . If you change your mind about an answer, put a line through the box  and then mark your new answer with a cross .
Plants have areas of undifferentiated cells called meristems. Cells in these areas divide rapidly during plant growth.
The photograph shows a cell undergoing nuclear division, as seen using a light microscope.

(i)  Which stage of nuclear division is shown in cell A?
(1)
   A    anaphase
   B    metaphase
   C    prophase
   D    telophase

(ii)  The mean distance between the two sets of chromatids in the photograph of cell A is 1.5 cm.
Calculate the actual distance in μm.
(2)

 ........................................................... μm
(iii)  Devise an investigation to study the effect of temperature on the rate of nuclear division in a plant meristem.
(5)
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(Total for question = 8 marks)

Q3.
 
A student prepared a root tip squash to view stages of mitosis.
The diagram shows the drawing made by the student.

(a)  The ratio of cells in the drawing showing anaphase compared to those showing metaphase is
(1)
   A    2:1
   B    1:2
   C    1:1
   D    3:1

(b)  The mitotic index is the percentage of cells undergoing mitosis.
The student calculated the mitotic index at different distances from the root tip. 
She used this information to plot the graph shown.

Calculate the distance from the root tip of the cells in the student's drawing.
(2)

Answer ...........................................................

(Total for question = 3 marks)

Q4.
 
Cell division can be affected by various chemicals. The effects of these chemicals can be studied by observing tissues.
The photograph shows onion root cells undergoing mitosis.

(i)  Draw a line labelled M to one cell at metaphase and a line labelled A to one cell at anaphase.
(2)
(ii)  The rate at which cells are dividing can be determined by calculating the mitotic index.
The mitotic index is the percentage of cells in a sample undergoing mitosis.
The table shows the number of cells at different stages of the cell cycle in one sample.

Calculate the mitotic index for the sample of cells shown in the table.
(2)

Answer ........................................................... %
 
(Total for question = 4 marks)

Q5.
The photograph below shows plant cells at different stages in the cell cycle.

(a)  Name the stage of mitosis shown by each of the cells labelled X and Y.
(2)
X .................................................................................................................................................... 
Y .................................................................................................................................................... 

(b)  Describe what occurs during prophase.
(4)
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(c)  Cell Z is not undergoing mitosis.

Suggest which stage of the cell cycle it is undergoing. 
Give a reason for your answer.
(2)
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(Total for Question = 8 marks)

Mark Scheme

Q1.

 

Q2.

 

Q3.

Q4.

 

Q5.