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Screening tests for identifying gene products for establishing the existence of
a disease (methods such as protein truncation) – autosomal recessive diseases
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The test is performed on the patients themselves – even if there is only one. These
tests involve examining the soundness of the gene products, i.e. the proteins, without
examining the sequence of bases, so that the mutation itself is not demonstrated.
The result can establish the existence of the disease being investigated.
This is a short, simple and more rapid test than establishing the entire gene sequence.
However, it cannot always serve as a prenatal diagnostic tool. It is advisable to
test for the exact defect afterwards.
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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