Difference between revisions of "Cytogenetics"

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****Examples: Q-banding (Q=Quinacrine), C-banding (C=constitutive heterchromatin), G-banding (G=Giemsa), R-banding (R=reverse).
****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.
*****Q-banding is the standard at UHN.
Analysis:
*Based on comparison to maps of the chromosomes (ideograms).
**Detailed ideograms are in ''ISCN 2009''.<ref>{{Ref ISCN2009|}}</ref>
***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.<ref name=pmid8291552>{{Cite journal  | last1 = Welborn | first1 = JL. | last2 = Welborn | first2 = R. | title = Banding resolution of human chromosomes: a method of accuracy and simplicity. | journal = Am J Med Genet | volume = 47 | issue = 8 | pages = 1180-3 | month = Dec | year = 1993 | doi = 10.1002/ajmg.1320470810 | PMID = 8291552 }}
</ref>


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Revision as of 18:20, 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

  • 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:

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.

External links

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