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Screening tests for identifying gene products for establishing the existence of
a disease (methods such as protein truncation) – X-linked 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 (especially
male ones) are healthy or affected.
- To establish which females in the family carry the mutation and who are therefore
considered to be carriers but not affected. Women found to be carriers can undergo
prenatal tests in every pregnancy in order to establish whether or not the fetus
is affected.
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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