Investigation methods
GTG-banding (G-bands by trypsin using Giemsa)
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Principle:
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Through the treatment with trypsin and subsequent staining of fixed metaphase chromosomes with giemsa a reproducible black and white banding pattern is generated. |
| Significance: | GTG banding is a standard method for conventional chromosome analysis that can detect numerical and structural chromosome anomalies. |
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Remarks:
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The management of diagnostics and the reports are in accordance to the guidelines of the "Berufsverband Medizinische Genetik e.V." with a minimum of 400 bands per haploid karyotype in pre and postnatal diagnostics (Verlag Medizinische Genetik Sonderdruck, 7. Auflage Okt. 2001, S. 57-58). The cytogenetic laboratory of the institute of Human Genetics and Anthropology takes part in quality management and interlaboratory tests. |
CBG-banding (G-bands by Barium hydroxide using Giemsa)
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Principle:
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Through an alkali lyses by bariumhydroxid and subsequent staining of fixed metaphase chromosomes with giemsa a specific banding pattern is generated. |
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Significance:
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CBG-banding is used to stain heterochromatic regions like centromeres, satellites of acrocentric chromosomes and the heterochromatic regions of chromosomes 1, 9, 16 and Y.. |
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Remarks: |
This method is used in all postnatal investigations and could be applied in addition to GTG also in prenatal cases to clarify a heterochromatic regionk. |
NOR-Färbung
| Principle: | Through a staining with silvernitrate the nucleolus organizing regions are painted. |
| Significance: | NOR-staining is used to evaluate the satellite stalks of acrocentric chromosomes (13,14,15,21,22). |
| Remarks: | This method is employed in pre- and postnatal cytogenetics in cases of enlarged or structural rearranged short arms of acrocentric chromosomes. |
Limits of conventional cytogenetic diagnostic
The result of a chromosome analysis gave a high but no absolute guarantee. The result is limited on microscopally visible chromosome rearrangements. Submicroscopic changes and aberrations that are rare or changes on DNA sequence and DNA modifications like epigenetic ones (e.g.: Uniparentale Disomien) are not detectable with conventional cytogenetic methods. Furthermore chromosome analysis gave no hind on deseases in newborns, that are not caused by chromosome aberrations.
The options in chromosome diagnostics are increasing since the introduction of new methods like FISH and array CGH and better cell culture conditions. Therefore it makes sense to reinvestigate patients that were conventional cytogenetic analysed with a normal karyotype some years before, if the indication is still the same.
Important information for cytogenetic diagnostics
Prenatale:
Genetic counselling is recommended before the invasiv procedures in order to inform the women about the procedure, options and limits of the method. In case of an abnormal result genetic counselling is strongly recommended.
Genetic counselling is also offered from our institution (genetic counselling).
For the following indications a prenatal chromosome analysis can be helpful:
- advanced maternal age (>35 years)
- psychological reasons
- higher risk after triple test
- higher risk after first trimester screening
- rearranged chromosomes in one parent
- trisomies/chromosome aberrations in the near kinship
- aberrant karyotype in a previously pregnancy
- neural tube abnormality in a previously pregnancy
- missed abortion
- supposed microdeletion syndrome like CATCH 22 in connection with heart defects (FISH)
- ultrasound abnormalities like:
- white spot in the heart
- plexuscyst
- growth retardation
- pyelektasy
- increased nuchal translucency
- absence of as nasale
- echogenic intestine (hind for cystic fibrosis)
- hydrops fetalis ect.
Postnatale:
- dysmorphic signs / malformations (e.g. face, hand, ear, feet)
- physical and mental retardation
- indifferent sex
- short stature, primary amenorrhoea, hypogonadism, high stature (e.g. Turner-, Klinefelter-, triple X-Syndrom)
- infertility, planed ICSI
- two or more abortions
- investigation of the parents , if an abnormal karyotype is found in the child
- • supposed microdeletion syndrome: (additional FISH and/or molecular diagnostics)
- Wolf Hirschhorn-Syndrome
- Cri-du-chat-Syndrome
- Williams-Beuren-Syndrome
- Rubinstein-Taybi-Syndrome
- Angelman-Syndrome
- Prader Willi-Syndrome
- Smith-Magenis-Syndrome
- Miller-Dieker-Syndrome
- CATCH 22 / DiGeorge-Syndrome
- Kallmann-Syndrome
- Deletion 1p36-Syndrome
- SRY (cryptic translocation)
- Down critical region (cryptic translocation) etc.
Specimen and duration
Prenatale:
We kindly ask for an advanced notification under 03641/9-396804 or 9-396834.
Every specimen should be attached to a covering letter(Begleitschein Pränatale Zytogenetik).
Specimen should be mailed uncooled by courier in the beginning of the week. Specimen mailed on Thursday or Friday needs to be announce by telephone. Please ensure that the probe material is safety packed. Known HIV or other infectious diseases should be indicated on the covering letter.
In case of an abnormal result genetic counselling is strongly recommended.
If you have any questions concerning cytogenetics, specimen, mailing, single diseases don't hesitate to ask for (03641/9-396830).
| Specimen | Duration | Remarks |
| amniotic fluid (ca. 10-20 ml) with or without AFP determination | ca. 8-14 days | a preliminary result is given by telephone after 6-9 days to the sender |
| fast test (STR-diagnostics for aneuploidies of chromosomes: 13,18,21,X,Y) | ca. 1-2 working days | only in combination with conventional cytogenetics |
| chorionic villi (ca. 10-40 mg in sterile media or sodium chloride solution) | 2 days direct preparation and 10-14 days long term culture | |
| fetal cord blood | ca. 2-5 days | (ca. 2 ml heparin-blood) always in combination with a Kleihauer-Betke-Test for fetal blood cells |
| abortion material (10-20 mg in sterile media or sodium chloride solution) | ca. 14-28 days |
We also offer an archiving of probes, DNA isolation or further sending to other laboratories please ask for details.
Postnatale:
Every specimen should be attached to a covering letter Begleitschein Postnatale Zytogenetik.
Specimen should be mailed uncooled by courier in the beginning of the week. Specimen mailed on Thursday or Friday needs to be announce by telephone. Please ensure that the probe material is safety packed. Known HIV or other infectious diseases should be indicated on the covering letter. Bei auffälligen Befunden ist eine genetische Beratung dringend angezeigt. Diese kann im hiesigen Institut erfolgen. In case of an abnormal result genetic counselling is strongly recommended (genetic counselling)
If you have any questions concerning cytogenetics, specimen, mailing, single diseases don't hesitate to ask for (03641/9-396830).
| Specimen | Duration | Remarks |
| Ca. 5 ml peripheral heparin-blood | ca. 10 days, urgent 2-4 days | |
| skin fibroblasts (in sterile media or sodium chloride solution) | ca. 14-28 days |
We also offer an archiving of probes, DNA isolation or further sending to other laboratories please ask for details.