What types of probes are used in fluorescence in situ hybridization (FISH)?

There are 3 major types of probes used in FISH, each of which has a different application:

• Locus specific probes: This type of probe binds to a particular region of a chromosome. These probes are useful in detection of microdeletion and microduplication syndromes within a particular chromosome.
• Repetitive probes: They are generated from the repetitive sequences found in the middle of each chromosome, which can be used to determine whether an individual has the correct number of chromosomes. When being used together with locus specific probes, these probes can be used to determine if an individual is missing genetic material from a particular chromosome.
• Whole chromosome probes: They are collections of small probes labeled with different fluorescent dyes, each of which binds to a different sequence along a given chromosome. These probes can be used to map the whole chromosome, providing information of chromosomal abnormalities.