Pollutants and the
environment
Bill Indge
Pollutants and the environment
Vitellogenin (VTG) production in the liver
Liver cell
Cytoplasm
Oestrogen
receptor
Nucleus
Ribosome
Gene
coding for
VTG
Pollutants and the environment
Vitellogenin (VTG) production in the liver
 Oestrogen
enters the
nucleus and
binds with
the oestrogen
receptor
Oestrogen
receptor
Ribosome
Gene
coding for
VTG
Pollutants and the environment
Vitellogenin (VTG) production in the liver
 The
activated
receptor now
attaches to the
target gene
Gene
coding for
VTG
 The DNA is
transcribed and
VTG mRNA is
produced
Pollutants and the environment
Vitellogenin (VTG) production in the liver
 The VTG
mRNA
migrates to
the ribosomes
in the
cytoplasm
Gene
coding for
VTG
Pollutants and the environment
Vitellogenin (VTG) production in the liver
 VTG is
synthesised
and secreted
from the liver
Gene
coding for
VTG
Pollutants and the environment
A laboratory-based investigation
The title of the original paper on which this exercise is based is:
Fathead minnow and bluegill sunfish life-stage responses
to 17 β-estradiol exposure in outdoor mesocosms
Sarah M. Elliott, Richard L. Kiesling, Zachary G. Jorgenson, Daniel C. Rearick,
Heiko L. Schoenfuss, Kim T. Fredricks and Mark P. Gaikowsk
Pollutants and the environment
In a laboratory-based investigation, sexually mature fathead minnows
were randomly divided into two groups — an experimental group and
a control group.
• A solution of synthetic oestrogen was added to the tank containing
the experimental group of fish. The resulting concentration of
oestrogen reflected environmental concentrations.
• A control solution was added to the tank containing the control
group.
1 Explain why it was important that the fish were randomly divided
into the two groups.
(2 marks)
1 The idea of preventing conscious choice;
This might influence results; [2]
Pollutants and the environment
In a laboratory-based investigation, sexually mature fathead minnows
were randomly divided into two groups — an experimental group and
a control group.
• A solution of synthetic oestrogen was added to the tank containing
the experimental group of fish. The resulting concentration of
oestrogen reflected environmental concentrations.
• A control solution was added to the tank containing the control
group.
2 A control solution was added to the tank containing the control
group of fish. What would you expect to be in this control solution?
Explain your answer.
(2 marks)
Think carefully about the nature of the control that is appropriate in this
investigation. With the information provided, ‘nothing’ would be an
inappropriate response.
‘Water’ might be a standard answer but it makes assumptions about the
composition of the synthetic oestrogen solution.
Pollutants and the environment
In a laboratory-based investigation, sexually mature fathead minnows
were randomly divided into two groups — an experimental group and
a control group.
• A solution of synthetic oestrogen was added to the tank containing
the experimental group of fish. The resulting concentration of
oestrogen reflected environmental concentrations.
• A control solution was added to the tank containing the control
group.
2 A control solution was added to the tank containing the control
group of fish. What would you expect to be in this control solution?
Explain your answer.
(2 marks)
2 Everything that was added to the fish in the experimental tank
other than the synthetic oestrogen;
This ensures that any difference would result from the oestrogen/
would not be the result of other substances in the solution; [2]
Pollutants and the environment
Some differences between fathead minnows treated with
synthetic oestrogens and controls
Treated with
synthetic oestrogen
Control
1.07
1.10*
0.802
0.761
1.55
1.35*
2
3*
Body condition factor
total mass/g × 100 000
total length3
Gonadosomatic index
testis mass/g × 100
body mass/g
Hepatosomatic index
liver mass/g × 100
body mass/g
Secondary sexual characters
index
* Significantly different, p<0.01
Pollutants and the environment
Treated with
synthetic oestrogen
Control
1.55
1.35*
Hepatosomatic index
liver mass/g × 100
body mass/g
* Significantly different, p<0.01
3 One of the control fish had a hepatosomatic index of 1.35. The body
mass of this fish was 2.73 g. Calculate the mass of its liver.
Show your working.
(2 marks)
Remember
• If you don’t attempt the question, you cannot gain credit.
• Show your working: you can gain marks even if the answer is wrong.
• Use some common sense…the liver won’t weigh more than the fish!
Pollutants and the environment
Treated with
synthetic oestrogen
Control
1.55
1.35*
Hepatosomatic index
liver mass/g × 100
body mass/g
* Significantly different, p<0.01
3 One of the control fish had a hepatosomatic index of 1.35. The body
mass of this fish was 2.73 g. Calculate the mass of its liver.
Show your working.
(2 marks)
3 2 marks for correct answer of 0.04 g;
1 mark for incorrect answer but clearly showing that the calculation is
based on the formula: hepatosomatic index = liver mass × 100;
body mass
Pollutants and the environment
Treated with
synthetic
oestrogen
Control
0.802
0.761
Gonadosomatic index
testis mass/g × 100
body mass/g
4 The testis mass is given as an index. Explain why it was given as an
index, not the actual mass. (2 marks)
4 Allows results to be compared/standardised/body size
to be taken into consideration;
Because testis mass will vary with body mass/larger fish
will have larger testes;
[2]
Pollutants and the environment
Treated with
synthetic oestrogen
Control
1.55
1.35*
Hepatosomatic index
liver mass/g × 100
body mass/g
* Significantly different, p<0.01
5 The scientists who carried out this investigation reported that large
protein-containing vesicles had accumulated in the cytoplasm of the
liver cells in a significant number of the experimental group of fish.
(a) Explain how the data in the table support this observation.
(2 marks)
5(a) The experimental/oestrogen-treated group have a (significantly)
higher hepatosomatic index;
(Larger liver) caused by the protein-containing vesicles;
[2]
Pollutants and the environment
Treated with
synthetic oestrogen
Control
1.55
1.35*
Hepatosomatic index
liver mass/g × 100
body mass/g
* Significantly different, p<0.01
5(b) Use your knowledge of the way in which oestrogen affects
vitellogenin production to explain the presence of the proteincontaining vesicles in the liver cells of the experimental group of fish.
(3 marks)
5(b) Binds with oestrogen receptors present in liver cells;
Stimulates transcription of VTG mRNA;
VTG protein synthesised;
VTG accumulates in vesicles in liver cells; [3 max]
Pollutants and the environment
Treated with
synthetic oestrogen
Control
1.07
1.10*
0.802
0.761
1.55
1.35*
2
3*
Body condition factor
total mass/g × 100 000
total length3
Gonadosomatic index
testis mass/g × 100
body mass/g
Hepatosomatic index
liver mass/g × 100
body mass/g
Secondary sexual characters
index
* Significantly different, p<0.01
6 Using only data from the table, explain why synthetic oestrogens may
affect the reproductive success of male fathead minnows. (4 marks)
Pollutants and the environment
Treated with
synthetic oestrogen
Control
1.07
1.10*
Body condition factor
total mass/g × 100 000
total length3
Mating success is likely to depend
on body condition/Males with
poorer body condition likely to
have lower mating success;
* Significantly different, p<0.01
6 Using only data from the table, explain why synthetic oestrogens may
affect the reproductive success of male fathead minnows. (4 marks)
Pollutants and the environment
Treated with
synthetic oestrogen
Control
0.802
0.761
Gonadosomatic index
testis mass/g × 100
body mass/g
The difference in gonadosomatic index
is not significant/The oestrogentreated fish have significantly lower
body condition and secondary sexual
characters index;
* Significantly different, p<0.01
6 Using only data from the table, explain why synthetic oestrogens may
affect the reproductive success of male fathead minnows. (4 marks)
Pollutants and the environment
Treated with
synthetic oestrogen
Control
Larger liver in oestrogentreated males likely to be
linked to high vitellogenin
production;
Hepatosomatic index
1.55
1.35*
liver mass/g × 100
body mass/g
* Significantly different, p<0.01
6 Using only data from the table, explain why synthetic oestrogens may
affect the reproductive success of male fathead minnows. (4 marks)
Pollutants and the environment
Treated with
synthetic oestrogen
Control
Secondary sexual character
important in courtship/defence
of territory;
Secondary sexual
characters index
2
3*
* Significantly different, p<0.01
6 Using only data from the table, explain why synthetic oestrogens may
affect the reproductive success of male fathead minnows. (4 marks)
Pollutants and the environment
A field-based investigation
The title of the original paper on which this exercise is based is:
Collapse of a fish population after exposure to a
synthetic estrogen
Karen A. Kidd, Paul J. Blanchfield, Kenneth H. Mills, Vince P. Palace,
Robert E. Evans, James M. Lazorchak and Robert W. Flick
Pollutants and the environment
The protocol
Control lake (B)
Experimental lake (A)
2 years prior to
starting treatment
No synthetic
oestrogen added
3 years of
treatment
Regular addition of
synthetic oestrogen
2 years after
treatment stopped
Measurements collected from fathead minnows from
both lakes of
• concentration of the egg protein vitellogenin (VTG)
• concentration of vitellogenin mRNA
• numbers and lengths of fish
Pollutants and the environment
Lake B
6000
4000
2000
Lake A
3
2
Year
2003
2002
2001
2000
2003
2002
0
2001
1
2000
Concentration of VTG/
arbitrary units
The concentration of VTG in whole-body homogenate samples of
male fathead minnows captured during the spring of each of the
years shown
6000
4000
2000
Lake B
Lake A
3
2
2003
2002
2001
2000
2003
2002
0
2001
1
2000
Concentration of VTG/
arbitrary units
Pollutants and the environment
1 Explain the advantage of the break in the y-axis on this graph.
2 Explain what is meant by a whole-body homogenate.
(1 mark)
(2 marks)
1 Allows a wide range of values/high and low values to be plotted/read
accurately;
[1]
2 In homogenate the cells have been mechanically disrupted;
In this case the whole fish/all tissues homogenised;
[2]
6000
4000
2000
Lake B
Lake A
3 Explain the
difference in the
results for lakes
A and B.
(3 marks)
3
2
2003
2002
2001
2000
2003
2002
0
2001
1
2000
Concentration of VTG/
arbitrary units
Pollutants and the environment
3 Lake B and lake A in 2000 and 2001 show natural variation/small
differences may not be significant;
Synthetic oestrogen added to lake A in 2002;
Stimulates secretion of VTG by liver;
Carried by blood to all organs (so homogenate concentration
increases);
[max 3]
Pollutants and the environment
Numbers of fish given as a population index
Mean population index
Year
Control lake (B)
Experimental lake (A)
1999
490.3
180.0
2000
19.1
50.3
2001
56.1
117.7
2002
9.6
0.7
2003
20.6
2.6
2004
51.9
0.1
2005
355.9
0.1
Addition
of
synthetic
oestrogen
Pollutants and the environment
Mean population index
Year
Control lake (B)
Experimental lake (A)
1999
490.3
180.0
2000
19.1
50.3
2001
56.1
117.7
2002
9.6
0.7
2003
20.6
2.6
2004
51.9
0.1
2005
355.9
0.1
4 Explain why
the figures
were given as
the population
index and not
as the total
population.
(1 mark)
5 Describe
the results
shown in the
table.
(3 marks)
4 Difficulty of obtaining an accurate/reliable count; [1]
5 Variable population in lake B, and in lake A before treatment;
In 2002/year after treatment large drop in population of lake A;
Population in lake A after treatment stays low/does not recover; [3]
Pollutants and the environment
Measuring fathead minnows
Fork length
6 Fork length gives
a more reliable
measurement of
the length of the
fish than total
length. Suggest
why.
(1 mark)
Total length
6 The ends of the tail may be worn/two lobes of tail fin may be
different lengths;
[1]
Pollutants and the environment
Lake B
Lake A
2000
2002
Number of
fish
Number of Number of
fish
fish
Histogram showing lengths of fish
2004
Fork length
Fork length
Pollutants and the environment
Number of Number of
fish
fish
Histogram showing lengths of fish
Lake B
Lake A
2000
Number of
fish
2002
2004
Fork length
7(a) Few fathead minnows live
beyond 2 years. In any given
year there are young fish that
hatched that year and mature
fish that hatched in the
previous year. Explain how the
histograms support this
information.
(1 mark)
Pollutants and the environment
Number of Number of
fish
fish
Histogram showing lengths of fish
Lake B
Lake A
2000
Number of
fish
2002
2004
Fork length
7(a) The histogram is
bimodal/contains two peaks,
suggesting two classes of
fish.
[1]
Pollutants and the environment
7(b) Use the data from the table
to explain the results for 2002 in
lake A. (3 marks)
7(b) The table shows the large
decrease in population the year
after the addition of synthetic
oestrogen;
Lake A
2000
2002
Histogram shows no young fish
hatch in 2002;
Small number in histogram the
result of few fish hatching in 2001;
[3]
2004
Fork length
Pollutants and the environment
Collapse of a fish population after exposure to a synthetic
estrogen
Karen A. Kidd, Paul J. Blanchfield, Kenneth H. Mills, Vince P. Palace,
Robert E. Evans, James M. Lazorchak and Robert W. Flick
But also…
• Feminising males means extinction
• Fish devastated by sex-changing chemicals in municipal
wastewater
• Because of oestrogen, Canadian fish are too ‘confused’ to
mate
• Birth control for fish