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Concept explainers
Recall that Leber congenital amaurosis (LCA), a form
of congenital blindness in humans, can be caused by
homozygosity for recessive mutations in the RPE65
gene. Recently, a rare dominant mutation in RPE65
has been implicated as one cause of an eye disease
called retinitis pigmentosa, which is characterized by
retinal degeneration that can progress to blindness.
The dominant RPE65 mutation is a missense mutation causing amino acid 447 in the polypeptide to
change from Asp to Glu. Little is known about the
nature of the mutant protein.
a. Do you think that the dominant allele is more
likely a loss-of-function or a gain-of-function
mutation? Explain.
b. As described in this chapter, gene therapy for LCA
has been at least partially successful. Do you think
that the same kind of gene therapy can be used for
patients with retinitis pigmentosa caused by the
dominant mutant allele of RPE65? Explain.
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