1 a) If a man and a woman, both heterozygous for the gene for cystic fibrosis, decide to have children, what is the probability that their children will develop the condition?
b) Explain how gene therapy is being used to help cystic fibrosis sufferers. Introducing the gene using viral vectors has not been particularly successful. What problem has there been?
c) What is meant by the terms i) genetic counselling and ii) genetic screening?
d) As well as affecting the mucus in the lungs, cystic fibrosis also affects the mucus in the gut. The mucus may block the tube leading from the pancreas to the small intestine. How would this affect digestion? What might be the long term effects of this?
e) Give examples of other disorders inherited via i) recessive genes and ii) dominant genes.
f) In the future, we may all be able to have our genetic make-up analysed to identify the diseases from which we are most at risk. Apart from the medical professions, organisations such as insurance companies would be very interested in such information. Discuss the advantages and disadvantages of having such detailed genetic information available.
2 The ripening of fruit is due in part to the enzyme polygalacturonidase, which breaks down pectin. Pectin forms part of the middle lamella that cements the cell walls of adjacent cells together.
a)What chemical building blocks make up i) cellulose, ii) pectin and iii) protein?
b) Explain why the ripening process will be slowed down if polygalacturonidase is not produced or if the enzyme structure has
been changed.
c) Explain (using a mock DNA base sequence) why reversing a gene will make the message of that gene 'non-sense'.
d) Why do you think that the regulations concerning genetically
engineered organisms are so restrictive?
e) Is genetic engineering of organisms better or worse than manipulating their genetic make-up by selective breeding?
f) Does the fact that we have the technology to change things at a genetic level justify our doing so?
