Biology 9700 · AS & A Level · Genetic technology applied to medicine

Genetic technology applied to medicine — practice question

In humans, the gene RPE65 codes for a protein that rebuilds visual pigment in rod and cone cells after light exposure. A recessive allele of this gene leads to reduced vision from birth, which then develops into total blindness in early adulthood. This disorder is known as LCA. In 2008, trials investigated whether LCA could be treated safely using gene therapy.
(a)[3]

Suggest and explain why gene therapy is suitable for treating LCA.

(b)[2]

Six adults with this condition took part in the study. Genetically modified adenoviruses (a type of virus that can cause respiratory infections) were used as vectors. The vectors were injected beneath the retina of one eye of each participant. Suggest two ways in which the genome of the adenoviruses used as vectors would be different from that of normal adenoviruses.

(c)[2]

All the participants showed improvements in vision, but the very small sample size meant that most of these improvements were not statistically significant. Suggest why these trials were planned to include such a small number of participants.

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