Difference between revisions of "Cytogenetics"

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This article deals with '''cytogenetics'''.
This article deals with '''cytogenetics'''.


==General==
=General=
*Large changes (chromosomal).
*Large changes (chromosomal).
**Maximum resolution 3-4 megabase pairs (3-4 million base pairs); may be less - dependent on band density.<ref>{{Ref WMSP|695}}</ref>
**Maximum resolution 3-4 megabase pairs (3-4 million base pairs); may be less - dependent on band density.<ref>{{Ref WMSP|695}}</ref>
*Morphologic data.
*Morphologic data.


==Techniques==
=Techniques (overview)=
*ISH = in situ hybridization.
*ISH = in situ hybridization.
**FISH = fluorescent in situ hybridization.  
**FISH = fluorescent in situ hybridization.  
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*Karyotyping.
*Karyotyping.


===Karyotyping===
==Karyotyping==
What?
What?
*Metaphase nuclei.
*Metaphase nuclei.
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*Quinacrine dye - AT-rich regions brighter than GC-rich regions.
*Quinacrine dye - AT-rich regions brighter than GC-rich regions.


===ISH===
==ISH==
*Usu. interphase nuclei.
*Usu. interphase nuclei.


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*Cultured cells.
*Cultured cells.


====Probe types====
===Probe types===
Types:
Types:
*Fusion (two colours).
*Fusion (two colours).
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*[http://commons.wikimedia.org/wiki/File:Bcrablmet.jpg Bcr-Abl translocation (WC)].
*[http://commons.wikimedia.org/wiki/File:Bcrablmet.jpg Bcr-Abl translocation (WC)].


==See also==
===Tests===
====ERBB2====
*[[AKA]] HER2,<ref>{{OMIM|164870}}</ref> AKA HER2/neu.
*Important in [[invasive breast cancer]].
 
Protocol:
*ISH label for HER2.
*ISH label for CEP17 (D17Z1 -- labels centromere of chromosome 17).<ref>URL: [http://www.medscape.com/viewarticle/546925_3 http://www.medscape.com/viewarticle/546925_3]. Accessed on: 10 May 2011.</ref>
*In 60 nuclei:
**Count number of HER2 signals.
**Count number of CEP17 signals.
*Calculate ratio HER2/D17Z1 signals:
**>2.2 --> HER2 amplification.
 
=See also=
*[[Molecular pathology]].
*[[Molecular pathology]].
*[[Chromosomal translocations]].
*[[Chromosomal translocations]].


==References==
=References=
{{Reflist|2}}
{{Reflist|2}}


==External links==
=External links=
*[http://homepage.mac.com/wildlifeweb/cyto/human/ Cytogenetics (homepage.mac.com)] - has ideograms (banding maps) of the human chromosomes.
*[http://homepage.mac.com/wildlifeweb/cyto/human/ Cytogenetics (homepage.mac.com)] - has ideograms (banding maps) of the human chromosomes.


[[Category:Molecular pathology]]
[[Category:Molecular pathology]]

Revision as of 18:36, 10 May 2011

This article deals with cytogenetics.

General

  • Large changes (chromosomal).
    • Maximum resolution 3-4 megabase pairs (3-4 million base pairs); may be less - dependent on band density.[1]
  • Morphologic data.

Techniques (overview)

  • ISH = in situ hybridization.
    • FISH = fluorescent in situ hybridization.
    • SISH = silver in situ hybridization.[2]
  • Karyotyping.

Karyotyping

What?

  • Metaphase nuclei.

How?

  • Chromosomes are identified by:
    • Size (chromosome 1 = largest, chromosome 22 = smallest).
    • Position of centromere.
    • Banding pattern - using (special) stains:
      • Several different techniques (stains) are used:[3]
        • Examples: Q-banding (Q=Quinacrine), C-banding (C=constitutive heterchromatin), G-banding (G=Giemsa), R-banding (R=reverse).
          • Q-banding is the standard at UHN.

Analysis:

  • Based on comparison to maps of the chromosomes (ideograms).
    • Detailed ideograms are in ISCN 2009.[4]
      • The detail of an ideogram is given in "band levels"; a 850 band ideogram has a higher resolution than a 400 band ideogram. The typical range for band level is 300-850. The band level, for a given specimen, is determined by an empirical standard and based on the number of bands an observer sees in a subset of the chromosomes.[5]

Image:

Notes:

  • Quinacrine dye - AT-rich regions brighter than GC-rich regions.

ISH

  • Usu. interphase nuclei.

May be prepared from:

  • In situ paraffin sections (section 4 micrometers thick).
  • Isolated nuclei (section 10 micrometers thick).
  • Cytospin.
  • Cultured cells.

Probe types

Types:

  • Fusion (two colours).
  • Breakapart (two colours).
  • Deletion/duplication (e.g. trisomy).

Image:

Tests

ERBB2

Protocol:

  • ISH label for HER2.
  • ISH label for CEP17 (D17Z1 -- labels centromere of chromosome 17).[7]
  • In 60 nuclei:
    • Count number of HER2 signals.
    • Count number of CEP17 signals.
  • Calculate ratio HER2/D17Z1 signals:
    • >2.2 --> HER2 amplification.

See also

References

  1. ↑ Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 695. ISBN 978-0781765275.
  2. ↑ URL: http://www.immunoportal.com/modules.php?name=News&file=article&sid=186. Accessed on: 2 May 2011.
  3. ↑ URL: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC355922/. Accessed on: 10 May 2011.
  4. ↑ Shaffer, Lisa G.; Slovak, Marilyn L.; Campbell, Lynda J. (2009). ISCN 2009: an international system for human cytogenetic nomenclature (2009 ed.). S. Karger AG. ISBN 978-3805589857.
  5. ↑ Welborn, JL.; Welborn, R. (Dec 1993). "Banding resolution of human chromosomes: a method of accuracy and simplicity.". Am J Med Genet 47 (8): 1180-3. doi:10.1002/ajmg.1320470810. PMID 8291552.
  6. ↑ Online 'Mendelian Inheritance in Man' (OMIM) 164870
  7. ↑ URL: http://www.medscape.com/viewarticle/546925_3. Accessed on: 10 May 2011.

External links

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