The following questions have been selected to test and consolidate your learning in this area of the CfE Higher syllabus. They will also help you understand the style of question you may encounter in your final exam. The answers for each question can be accessed by clicking to reveal. At the bottom of the section are the relevant homework sheets for this section. The answers can be accessed by clicking the marking guide link. Remember, practice in applying your learning is key to building your confidence and knowledge and improving your eaxm success.
1. Thalassaemia is the name of a group of inherited blood disorders that affect the body’s ability to produce haemoglobin in red blood cells. Red blood cells are produced in bone marrow.
Oxygen in the lungs binds to haemoglobin and is carried to the cells of the body to be used in respiration.
Beta thalassaemia is the result of a mutation in the gene coding for the β chain of haemoglobin. If a person inherits gene mutations from both parents, this person will show symptoms of anaemia and will require blood transfusions. Symptoms of anaemia include tiredness and breathlessness.
*(a) Using the information given above and your knowledge of gene mutation, suggest why a person with beta thalassaemia has symptoms of anaemia.
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2. (a) Cystic fibrosis (CF) in humans is caused by mutations of a gene coding for transmembrane protein (CFTR) which acts as an ion pump. A large number of different mutations of the gene have been found. Explain what is meant by a gene mutation.
(b) CFTR regulates the transport of chloride ions (Cl-) across the plasma (cell surface) membrane. Tissues that express the normal CFTR allele secrete alkaline fluids, whereas the secretions of tissues expressing some mutant alleles are acidic.
The transport of Cl- by epithelial cells expressing the normal CFTR allele was comparedwith that by epithelial cells expressing one of 10 different mutant CFTR alleles. The results are shown in table 2.1.
In the table, normal digestive functioning of the pancreas associated with a particular allele is indicated with a tick () and the absence of normal functioning by a cross ().
With reference to the information given in the table, explain why some mutant CFTR alleles allow normal digestive functioning of the pancreas and others do not.
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a) a change in the sequence/ order of bases of (genetic material)
b) 1. mutation may give different, amino acid / primary structure;
2. some mutations alter, molecular shape / tertiary structure / binding
3. non – functioning/ poorer functioning proteins so increase in acidity / decrease in pH;
4. effect on enzyme(s) /ref pH optimum of enzyme(s); poor digestion
5. Reference to table data e.g. some mutations, give some transport / have less effect (on digestion). >33% (of norm) allows normal digestive function / < 6% [A very low] does not.
