Final answer:
If the FISH test with a centromer 13 probe is positive for Patau syndrome (trisomy 13), it will result in three signals per nucleus.
Step-by-step explanation:
If the FISH test with a centromer 13 probe is positive for Patau syndrome (trisomy 13), it will result in three signals per nucleus.
The FISH (Fluorescence in situ hybridization) test uses fluorescent probes to bind to specific regions of the chromosome. In this case, the centromer 13 probe will bind to the centromere region of chromosome 13. If there is an extra copy of chromosome 13 (trisomy 13), there will be three signals instead of the normal two signals per nucleus.