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 the visual pigment in rod and cone cells after exposure to light. A recessive allele of this gene leads to poor vision from birth, which worsens until complete blindness in early adulthood. This condition is known as LCA. In 2008, trials investigated whether gene therapy could treat LCA safely and effectively.
(a)[3]

Suggest and explain why LCA is suitable for treatment using gene therapy.

(b)[2]

Six adults who had this condition took part in the study. Genetically modified adenoviruses (a type of virus capable of causing respiratory infections) served as vectors. Each participant received an injection of the vectors beneath the retina of one eye. Suggest two ways in which the genome of the adenoviruses used as vectors would differ from that of normal adenoviruses.

(c)[2]

Vision improved in all the participants, but because the trials involved only a small number of people, most of these gains were not statistically significant. Suggest why these trials were planned with such a small number of participants.

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