Homework task HB2.28.1
Lesson reference: B2.28 Genetic disorders
Genetic disorders
Learning objectives:
 Know that some disorders are inherited.
Suggested time:
30 minutes
Name: _______________________________ Date: ______________________
A Use the Internet and books to find out about the work of genetic counsellors:
i
What training/qualifications do they need?
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ii Do they work privately or for the National Health Service?
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iii What does their work involve?
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B Cystic fibrosis (CF) is the most common genetic disorder in the UK. About 1 in
20 people are carriers. This disorder is caused by a single gene defect. The
gene codes for a chloride ion channel protein in cells lining the airways,
digestive tract and reproductive tracts. The gene is on chromosome 7. The
protein it codes for is 1480 amino acids long. In most (70%) cases of CF, one
amino acid at position 508 is missing. However, there are more than 600 other
types of mutations of this gene that can lead to cystic fibrosis.
There is a test that can be done to identify carriers of the most common
mutation.
i
What percentage of people in the UK are carriers of cystic fibrosis?
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ii In the most common mutation of the gene on chromosome 7, how will the
DNA base pairs differ from those of the normal gene?
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iii Explain how the loss of an amino acid from the protein will affect the
protein’s ability to carry out its function:
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iv How many alleles are there in the human population for the CF gene?
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v Are people who suffer from cystic fibrosis homozygous or heterozygous?
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vi Are symptomless carriers of cystic fibrosis homozygous or heterozygous?
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vii What is the phenotype of someone who has the genotype Cc?
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© Oxford University Press 2011
This document may have been altered from the original.
263
C Red-green colour blindness is a recessive genetic disorder. It is rare and
affects more males than females. The gene for normal colour vision is on the X
chromosome.
i Why do you think this disorder is more common in males than in females?
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ii Explain why colour-blind males cannot pass this condition to their sons:
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© Oxford University Press 2011
This document may have been altered from the original.
264