Assessment task: Investigation
Laboratory investigation of pedigree pathways
(30 marks)
This laboratory investigation involves a family with a history of cardiovascular disease (CVD).
Your task is to predict those at risk of developing CVD when applying some laws of genetics.
You will also interpret a pedigree that outlines the inheritance of blood types and provide
explanations for certain circumstances. You should provide full setting out where required.
Section A: Polygenic problem CVD
(15 marks)
You are a medical scientist investigating CVD. Some recent studies have suggested that
there are six genes (3 pairs) that can contribute to the risk of CVD. Everyone has these
genes but we can inherit slightly different forms of them. Your task is to track these genes
over three generations of a family using a pedigree, then predict which members are most
likely at risk of developing CVD.
Instead of letters to represent genes, you will use colours.
What to do before you start:
1.
Print off the pedigree worksheet
2.
Obtain:

6 coloured pencils/markers

4 disposable cups

An assortment of coloured buttons (6 of each colour and can be any coloured
objects that match your coloured pens).
Part 1
1.
Choose a cup that will represent I 1 (grandmother). Put in 5 red buttons (5 ‘normal’
genes that do not contribute to CVD) and 1 blue button (1 gene that increases CVD risk).
2.
In the other cup (I 2 – grandfather) put in 3 red buttons (normal genes) as well as 1
orange, 1 green and 1 yellow button.
3.
On the pedigree, record the colour of the genes for the two grandparents. Use R = red,
O = orange, G = green and Y = yellow.
4.
Without looking, randomly draw 3 genes from each ‘grandparent’. This is the genetic
information being contributed to their first child.
5.
Record the colours of the genes on the pedigree.
6.
Return the genes to each grandparent cup (make sure the correct genes go to the
correct grandparent).
7.
Repeat steps 4–6 for each son or daughter in the second generation. Do not do this for
the son’s partner.
8.
Look at each individual’s 6 (CVD) susceptibility genes (their combination of buttons).
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Remember the genes that increase CVD risk are:
Part 2
1.
Place in a cup 6 genes that are the ones you drew for the second son in row 2.
2.
The partner of the second son is a ‘low risk’ woman. Put 5 red genes and 1 yellow to
represent her 6 CVD susceptibility genes.
3.
On the pedigree, colour the combination of genes carried by the partner of the second
son.
4.
This couple has children. Without looking, mix and randomly draw out 3 genes from
each parent. This will represent the genetic information inherited by their first child.
5.
On the pedigree colour the combination of genes that were passed onto the child.
6.
Return the genes to the parents and repeat steps 2 and 3.
7.
Label each individual that has been added to your pedigree as low, medium or high risk.
Part 3: Answer the following questions.
1.
The grandfather in this family was a ‘high-risk’ individual. How many of his children
were either medium or high risk? How many of his grandchildren were medium or high
risk?
(2 marks)
2.
Did the number of medium and high-risk individuals increase or decrease over
subsequent generations? Why do you think that happened?
(2 marks)
3.
In this activity you were able to label members as having a low, medium or high risk of
developing CVD. In reality, do you think it might be difficult to determine the risk? Why?
(2 marks)
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4.
What is the term given to traits that are the result of combined action of many genes and
the environment?
(1 mark)
5.
What are the important features to identify in a family health history? What is meant by a
‘close relative’?
(3 marks)
6.
Using a search engine, find out which chronic disease conditions can be predicted using
a genetic test.
(2 marks)
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Fill out the pedigree to show the family’s susceptibility to CVD.
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(3 marks)
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Section B: Pedigree pathways – Blood types
(15 marks)
1.
In the pedigree above, three family members have had their blood type identified. Write
down the genotypes for the following members:
a) II 3
b) I 2
c) III 1
(3 marks)
2.
What are the possible phenotypes for individual II 1?
3.
If individual II 4 was found to be blood type B what must his genotype be?
4.
What relationship describes III 1 and III 2?
(2 marks)
5.
What is the genotype and phenotype for III 2?
(2 marks)
6.
The parents of III 1 and III 2 divorced and each daughter went to live with separate
parents. Their father, a doctor, moved to Sub-Saharan Africa and spent 15 years there
treating the local people. Daughter III 1 went with him. When the sisters were eventually
reunited at their 18th birthday, many of their relatives didn’t recognise them as the very
‘similar’ sisters they were. Why would they no longer look identical? Explain using
epigenetics.
(5 marks)
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(2 marks)
(1 mark)
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