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CYTOGENETICS

Information

Cytogenetics is a special branch of genetics which deals  with the analysis of the chromosomes . Chromosome analysis may be performed on different tissues to identify clinically relevant chromosome abnormalities. The specimen is cultured and the harvested cells are stained (G-banding) and analysed  under the microscope for numeric and structural abnormalities. In order to optimise the diagnostic information obtained from a chromosome preparation, images of the individual chromosomes are arranged into a standardised format known as a karyotype or, more precisely, a karyogram.  The usual resolution of 4-10 Mb is often sufficient to confirm a clinical suspicion of a chromosomal abnormality.

Chromosome analysis on peripheral blood more information

  • Indication: Infertility or patients on IVF programs, two or more pregnancy losses, a previous child or a family H/O genetic / birth defect, consanguineous marriage, abnormal ultrasound findings, conspicuous prenatal karyotype of the unborn child, known familial chromosomal changes, abnormal growth patterns / retardation, ambiguous genitalia; early onset of puberty, dysmorphic features, mental and growth retardation, primary and secondary amenorrhea
  • TAT: 1-2 weeks
  • Specimen type: 2-5 ml peripheral blood in sodium heparin vial
  • Method: culture (48 h, 72 h),  G-banding karyotype analysis

Chromosome analysis on amniotic fluid  more information

  • Indication: Advanced maternal age (women 35 years of age or above), abnormal ultrasound findings,  positive first trimester test, positive triple test,  consanguineous marriage, parental chromosomal rearrangement, a previous child or a family H/O genetic / birth defect, birth of children with chromosomal aberration, birth of children with congenital malformations, maternal anxiety, mutagen exposure before or during pregnancy
  • TAT: 1-2 weeks
  • Specimen type: Amniotic fluid
  • Quantity: 10-15 ml in a sterile syringe. Do not centrifuge.
  • Method: Cell culture, preparation of chromosomes, G-banding karyotype analysis at the microscope

Chromosome analysis on chorionic villi sampling (CVS) more information

  • Indication: Early prenatal diagnostic (first trimester chromosome testing), advanced maternal age, two or more pregnancy losses, parental chromosomal structural changes, positive first trimester test, abnormal ultrasound findings, a previous child or a family H/O genetic / birth defect, mutagen exposure before or during pregnancy, single gene disorder, maternal anxiety
  • TAT: Preliminary results available within 6-24 hrs /  final test results available within 2-3 weeks
  • Specimen type: Chorionic villi
  • Quantity: 10-20 mg, in sterile transport medium or in sterile heparinized physiological NaCl solution. Do not centrifuge.
  • Method: Direct preparation or preparation after 24 h-culture, long-term culture, preparation of chromosomes, G-banding karyotype analysis at the microscope

Chromosome analysis from products of conception (POCs) more information

  • Indication: infertility or patients on IVF programs, missed abortion, two or more pregnancy losses, advanced maternal age, parental chromosome rearrangement (e.g. translocation), a previous child or a family H/O genetic / birth defect
  • TAT: 1-3 weeks

  • Specimen type: Products of conception including villi, placental biopsy, tissue, skin biopsy. Do not freeze.

  • Method: long-term culture, G-banded chromosome analysis, and/or flluorescence in situ hybridization (FISH), and/or aCGH

Information

As a special branch of cytogenetics, molecular cytogenetics offeres techniques to achieve even higher resolution of genomic changes. Fluorescence in situ hybridization (FISH) is a powerful molecular genetic approach to detect numerical as well as minor structural rearrangements potentially at the level of individual genes on all the body tissues. FISH identifies, dependent on the indication, specific chromosomal abnormalities by the presence or absence of fluorescently-colored signals in metaphase chromosomes or interphase nuclei. It is suitable for fetal aneuploidy, mosaicism and microdeletion syndromes.

Prenatal chromosome study with rapid screen for chromosomes X, Y, 13, 18, 21 more information

  • Chromosomal location: Xp11-q11 (DXZ1), Yp11-q11 (DYZ3), 13q14 (RB1), 21q22 (DSCR), 18p11-q11 (D18Z1)
  • Indication: advanced maternal age, abnormal ultrasound findings, positive first-trimester test, maternal anxiety, previous pregnancy with aneuploidy

  • TAT: 4-24 hrs

  • Specimen type: amniotic fluid or chorionic villi

  • Method: Preparation of native cells, fluorescence in situ hybridization (FISH) using specific fluorochrome-labeled probes for chromosomes 13, 18, 21, X, and Y, fluorescence microscopy

Microdeletion Diagnostic, Mosaic Diagnostic, Whole Chromosome Painting more information

  • Gene and location: Depends on the indication and preliminary findings. Wolf-Hirschhorn Syndrome (4p16.3), Cri-du-Chat Syndrome (5p15.2), Williams-Beuren Syndrome (7q11), Prader-Willi/Angelman Syndrome (15q11-q13), Lissencephaly/Miller-Dieker Syndrome (17p13.3), Smith-Magenis Syndrome (17p11.2), DiGeorge/Catch22 Syndrome (22q11.2), Kallmann Syndrome (Xp22.3), sex reversal (Yp11.23), X-linked Ichthyosis (Xp22.3), and others on request
  • Indication: Suspicion of microdeletion syndrome, detection of somatic mosaicism, characterization of complex chromosomal rearrangements

  • TAT: 1-5 days

  • Specimen type: peripheral blood (heparinized), amniotic fluid, chorionic villi, products of conception, mucosa cells, skin biopsy

  • Method: Cell culture, preparation of chromosomes, hybridization with appropriate fluorochrome-labeled DNA-probes, fluorescence microscopy

Subtelomere study to identify cryptic chromosomal imbalances more information

  • Location of FISH probes: specific subtelomeric regions of all chromosomes

  • Indication: abnormal growth patterns / retardation, dysmorphic features, mental and growth  retardation, multiple spontaneous miscarriages

  • TAT: 1-2 weeks

  • Material: 2-5 mLl peripheral blood, or other tissues

  • Method: Fluorescence in situ hybridization (FISH) analysis with subtelomere specific probes (whole panel) always in context with a standard chromosome analysis, single probe diagnostic on request

Contact person

Dr. rer. nat. Birgit Becker
Abteilung Zytogenetik

 

089 / 54 86 29 - 0

089 / 54 86 29 - 243

birgit.becker@synlab.com

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