What does FISH utilize to visualize copy number changes?

Fluorescence in situ hybridization (FISH) is a technique that employs fluorescence microscopy to detect and localize specific DNA sequences on chromosomes. It utilizes light-up probes, which are short segments of DNA that are labeled with fluorescent dyes. These probes bind to complementary sequences in the target DNA, allowing visualization of copy number changes, such as duplications or deletions of specific regions in the genome.

The light-up probes are essential because they illuminate the areas of interest directly on the chromosomes, making it possible to identify and quantify changes in chromosomal structure in a very precise manner. This feature is particularly useful in clinical genetics, such as in the diagnosis of genetic disorders and cancers, where specific chromosomal alterations can provide critical information for treatment and prognosis decisions.

In contrast, the other options do not directly align with the methodology of FISH. Whole genome sequencing involves reading the entire DNA sequence of an organism and does not focus on visualizing specific chromosomal regions. Massively parallel shotgun sequencing is a high-throughput sequencing method that generates a large amount of data without providing the specific localization of genetic changes within chromosomes. PCR amplification is a technique used to replicate specific DNA sequences but does not visualize or quantify those changes in the context of chromosomes. Thus,