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Finding the defect (mutation) by establishing the gene sequence – autosomal recessive
diseases
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The test is performed on the patients themselves. The mutation (the defect in the
gene) can be determined in the patient by establishing the gene sequence. If the
defect is found using this method, it is possible:
- To allow a couple that has had an affected child to undergo prenatal diagnosis to
determine with a high degree of reliability whether subsequent fetuses are healthy
or affected.
- To establish which family members carry the mutation and are therefore considered
to be carriers but not affected. Family members found to be carriers will be at
risk for having an affected child if their partners are also carriers, and therefore
their partners should also undergo testing for carrier status. However, gene sequence
testing on the partner is not simple – it is expensive, time-consuming, and not
completely reliable. Carrier testing involving examining the entire gene sequence
is not routinely performed.
If a patient cannot be examined:
It is impractical (but possible) to check family members (or the fetus) directly
using the same methods, which are time-consuming and complex.
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