Quantitative Fluorescent in situ hybridization (Q-FISH) is a cytogenetic technique based on the traditional FISH

Fluorescent in situ hybridization

FISH is a cytogenetic technique developed by biomedical researchers in the early 1980s that is used to detect and localize the presence or absence of specific DNA sequences on chromosomes. FISH uses fluorescent probes that bind to only those parts of the chromosome with which they show a high...

 methodology. In Q-FISH, the technique uses labelled (Cy3

Cyanine

Cyanine is a non-systematic name of a synthetic dye family belonging to polymethine group. Cyanines have many uses as fluorescent dyes, particularly in biomedical imaging...

 or FITC

Fluorescein isothiocyanate

Fluorescein isothiocyanate is a derivative of fluorescein used in wide-ranging applications including flow cytometry. FITC is the original fluorescein molecule functionalized with an isothiocyanate reactive group , replacing a hydrogen atom on the bottom ring of the structure...

) synthetic DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 mimics called peptide nucleic acid (PNA) oligonucleotides to quantify target sequences in chromosomal

Chromosome

A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...

 DNA using fluorescent microscopy

Fluorescence microscope

A fluorescence microscope is an optical microscope used to study properties of organic or inorganic substances using the phenomena of fluorescence and phosphorescence instead of, or in addition to, reflection and absorption...

 and analysis software. Q-FISH is most commonly used to study telomere

Telomere

A telomere is a region of repetitive DNA sequences at the end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes. Its name is derived from the Greek nouns telos "end" and merοs "part"...

 length, which in vertebrates are repetitive hexameric sequences (TTAGGG) located at the distal end of chromosomes.