FISH Techniques, FISH Probes and Their Applications in Medicine and Biology - An Overview
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In another approach, cross-species color banding probes from flowsorted, differently labeled gibbon chromosomes are utilized (Wienberg
et al. 1990, Wienberg and Stanton 1997). Because of an extensive sequence
homology (98%) between gibbon and human DNA and the many chromosomal rearrangements that have taken place during evolution, the hybridization of these probes onto human metaphases results in a specific
color banding pattern for each chromosome. This banding pattern has
been termed RxFISH and comprises a multi-color set of 110 distinct colored bars or "bands" per haploid chromosome set (Muller et al. 1997a,b).
Yet another bar-code approach is currently being exploited. By selecting a suitable panel of several microdissected overlapping chromosome
fragments from each human chromosome and using multicolor labeling,
each chromosome will acquire a characteristic bar-code appearance with
improved resolution (Chudoba et al. 1999). However, the technique is at
present only possible for a limited number of human chromosomes, but is
being made avaible for all.
Interphase cytogenetics
The term interphase cytogenetics was proposed by Cremer et al. in 1986
for analysis of interphase nuclei by in situ hybridization.
This method is a useful supplement to other cytogenetic approaches,
particularly when time is a crucial factor or for solid tumors in which metaphases are rarely seen or can only be produced with great difficulty.
Using combinations of various centromere specific probes, it is possible
to screen a large number of cells for numerical chromosomal aberrations
by counting the number of signals or spots in each nucleus. When, for
example, a probe for an autosome is used, two signals in each nucleus
are normally expected and when a cell contains a numerical aberration,
either one, three or more signals are expected. However, the interpretation
of such signals can be problematic. If, for example, only one spot is seen,
does this represent a true monosomy for that chromosome, or does it represent a spatial, but random, co-localization of the two centromeres in
that particular cell? Conversely, if three or more spots are seen does this
represent a true aneuploidy for that chromosome or does it represent an
artifact. Due to varying hybridization efficiencies in the sample and differences in cell cycle state, such normal variations must be encountered.
Two rules of thumb are used in practice to minimize these problems. One
is that if the two spots are separated by more than the diameter of the
largest spots, then they should be counted as two signals. The other
21
In another approach, cross-species color banding probes from flowsorted, differently labeled gibbon chromosomes are utilized (Wienberg
et al. 1990, Wienberg and Stanton 1997). Because of an extensive sequence
homology (98%) between gibbon and human DNA and the many chromosomal rearrangements that have taken place during evolution, the hybridization of these probes onto human metaphases results in a specific
color banding pattern for each chromosome. This banding pattern has
been termed RxFISH and comprises a multi-color set of 110 distinct colored bars or "bands" per haploid chromosome set (Muller et al. 1997a,b).
Yet another bar-code approach is currently being exploited. By selecting a suitable panel of several microdissected overlapping chromosome
fragments from each human chromosome and using multicolor labeling,
each chromosome will acquire a characteristic bar-code appearance with
improved resolution (Chudoba et al. 1999). However, the technique is at
present only possible for a limited number of human chromosomes, but is
being made avaible for all.
Interphase cytogenetics
The term interphase cytogenetics was proposed by Cremer et al. in 1986
for analysis of interphase nuclei by in situ hybridization.
This method is a useful supplement to other cytogenetic approaches,
particularly when time is a crucial factor or for solid tumors in which metaphases are rarely seen or can only be produced with great difficulty.
Using combinations of various centromere specific probes, it is possible
to screen a large number of cells for numerical chromosomal aberrations
by counting the number of signals or spots in each nucleus. When, for
example, a probe for an autosome is used, two signals in each nucleus
are normally expected and when a cell contains a numerical aberration,
either one, three or more signals are expected. However, the interpretation
of such signals can be problematic. If, for example, only one spot is seen,
does this represent a true monosomy for that chromosome, or does it represent a spatial, but random, co-localization of the two centromeres in
that particular cell? Conversely, if three or more spots are seen does this
represent a true aneuploidy for that chromosome or does it represent an
artifact. Due to varying hybridization efficiencies in the sample and differences in cell cycle state, such normal variations must be encountered.
Two rules of thumb are used in practice to minimize these problems. One
is that if the two spots are separated by more than the diameter of the
largest spots, then they should be counted as two signals. The other