Biology 9700 · AS & A Level · Principles of genetic technology
Principles of genetic technology — practice question
Leber’s congenital amaurosis (LCA) is an autosomal recessive disorder of the eye. LCA leads to eye disorders, including a severe reduction in vision at birth. LCA has been treated successfully with gene therapy, with a virus used rather than a plasmid as the vector. Adeno-associated virus (AAV) vectors carrying the therapeutic allele were injected straight into the retina, the layer at the back of the eye that contains the photoreceptor cells. The injection technique used to deliver the vectors carries a risk, because it could make the retina detach and so damage vision.
(a(i))[4]
Suggest the principal stages involved in producing recombinant DNA for this gene therapy example.
(a(ii))[2]
Explain why the fact that LCA is an autosomal recessive genetic disease means that it is appropriate for treatment by gene therapy.
(a(iii))[2]
Suggest why the retinal injection method of gene therapy was used for LCA before it was trialled on other retinal diseases that gradually reduce the vision of people as they get older.
(b(i))[3]
Suggest how errors that happen during PCR can lead to base substitution mutations in the DNA sequence of AAV.
(b(ii))[2]
Explain why the photoreceptor cells of the mouse fluoresced in step 3.
(b(iii))[1]
Predict the impact of the 7m8 AAV on treatment for age-related retinal diseases.
Worked solution & mark scheme
This 14-mark question has a full step-by-step worked solution and mark scheme.