In exons where sequencing did not reveal any variation between two alleles, Prevention cannot be certain that they were able to PCR amplify both of the patient’s alleles. Occasionally, a patient may carry an allele which does not amplify, due for example to a deletion or a large insertion. In these cases, the report contains no information about the second allele.
Similarly, Prevention sequencing tests have almost no power to detect duplications, triplications, etc. of the gene sequences.
Only the indicated exons and roughly 50 bp of flanking non-coding sequence on each side are analyzed. Test reports contain no information about other portions of the gene, including many regulatory regions.
In nearly all cases, Prevention is unable to determine the phase of sequence variants. In particular, when two likely causative mutations are found for recessive disorders, Prevention cannot be certain that the mutations are on different alleles.
Prevention’s ability to detect minor sequence variants, due for example to somatic mosaicism is limited. Sequence variants that are present in less than 50% of the patient’s nucleated cells may not be detected.
Runs of mononucleotide repeats (eg(A)n or (T)n) with n>8 in the reference sequence are generally not analyzed because of strand slippage during PCR and cycle sequencing.
Unless otherwise indicated, the sequence data that we report are based on DNA isolation from a specific tissue (usually leukocytes). Test reports contain no information about gene sequences in other tissues.