Molecular markers
Fluorescent in situ hybridization (FISH)
FISH probe patterns

Topic Completed: 1 January 2014

Minor changes: 15 February 2019

Copyright: 2003-2018,, Inc.

PubMed Search: FISH[TI] probe patterns

Nat Pernick, M.D.
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Table of Contents
Definition / general
Cite this page: Pernick N. FISH probe patterns. website. Accessed May 31st, 2020.
Definition / general
  • Following hybridization and washing, most probes are visualized by fluorescence when subjected to the proper excitation light wavelengths
  • Absence of signal:
    • Indicates deletion of the probe target (but need proper controls)
  • Extra signals:
    • May indicate trisomy or other aneuploidy
  • Fusion signal:
    • Two different fluorophores in close proximity often emit a third color (example red and green together emit yellow)
    • Examples:
      • Mantle cell lymphoma has diagnostic t(11;14)(q13;q32), which juxtaposes the 11q13 BCL1 gene locus next to the 14q32 immunoglobin sequence
      • If one locus is labeled green and the other red, a yellow signal indicates the translocation but separate green and red signals means no translocation
  • Split signal fluorescence:
    • Differently labeled probes flank a region broken in a specific translocation
    • With red and green probes but no translocation, two yellow signals will be seen (unaffected chromosomes) but with the translocation, separate green and red signals will be seen
  • Subdeletion signal fluorescence:
    • Two differently labeled probes are used
    • Red and green probes may be located flanking different possibly deleted areas
    • No deletion - two yellow signals
    • One deletion - one yellow signal and one red or green signal
    • Examples include Prader-Willi / Angelman, cri du chat, Williams and steroid sulfatase deficiency syndrome
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