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Basic genetics and patterns of inheritance
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
Various banding techniques are used to visualize the chromosomes. The most frequently used method is Giemsa banding or G-banding, which results in a specific pattern of dark and light bands on each chromosome. The older method, quinacrine banding, or Q-banding, produces the same dark and light patterns, but requires the use of a fluorescence microscope and is not used routinely. Reverse banding or R-banding, results in the opposite of the dark and light pattern seen with G-banding; this may be used to better see the ends of the chromosomes. C-banding stains the constitutive heterochromatin, which is near the centromeres and NOR stain visualizes the nucleolar organizing regions of the satellites and stalks of acrocentric chromosomes. For routine karyotype analysis, G-banding is typically used by most laboratories. Routine karyotyping cannot detect gains or losses of cytogenetic material smaller than about 4Mb in size and therefore can miss significant abnormalities.
Genetics in neonatal surgical practice
Published in Prem Puri, Newborn Surgery, 2017
As part of karyotype analysis, dividing cells in culture must be examined. These cells are usually lymphocytes (collected in lithium heparin), amniotic fluid cells, or fibroblasts. Cells are arrested in the metaphase stage of mitosis and stained in such a way that the chromosomes are easily visualized. The usual technique used is G-banding (using a Giemsa stain), which gives a characteristic positive and negative banding pattern to each chromosome. Each chromosome has a constriction, called a centromere, dividing the chromosome into a short arm (p) and a long arm (q). Each arm has a number of prominent bands, which can then be subdivided into smaller bands. The gene for the ABO blood group is localized to chromosome 9q34. The gene thus lies in the fourth subband from the centromere (q34) of the third band from the centromere (q34) on the long arm (q34) of chromosome 9 (9q34).
Genitalia, Ambiguous (Including Congenital Anomalies)
Published in Tony Hollingworth, Differential Diagnosis in Obstetrics and Gynaecology: An A-Z, 2015
A karyotype (chromosome analysis) is also done as an initial investigation. A fluorescent in situ hybridisation for the Y chromosome can be obtained within 48 hours in most places; however, a detailed karyotype (with G banding) often takes up to 1 week.
Substantial intrinsic variability in chemoradiosensitivity of newly established anaplastic thyroid cancer cell-lines
Published in Acta Oto-Laryngologica, 2020
Sigurdur Gretarsson, Alexander Nygren, Ann H. Rosendahl, Nektaria Mylona, Elisabeth Kjellén, Yuesheng Jin, Kajsa Paulsson, Åke Borg, Eva Brun, Jan Tennvall, Anders Bergenfelz, Lennart Greiff, Johan Wennerberg, Lars Ekblad
For cytogenetic analysis, cells were cultured in DMEM/F12 medium with 10% foetal bovine serum and antibiotics. When the mitotic index was high, cultured cells were exposed to colchicine (final concentration 0.03 µg/mL) for 4–5 h before harvesting. Cells were detached by trypsin EDTA (0.05%) and treated with hypotonic solution (0.06 mol/L KCl) for 35 min. Subsequently, the cells were fixed three times with methanol/acetic acid 3:1. Chromosome preparations were incubated at 60 °C overnight and then treated with 2 × SSC (saline sodium citrate buffer) in 60 °C water bath for 4 h. G-banding was done using Wright’s stain and karyotypes were described according to ISCN 2009. All cell lines were analysed for rearrangements of RET with metaphase fluorescence in situ hybridization according to standard methods, using break-apart probes and a whole chromosome paint probe for chromosome 10 (Abbott Molecular, Des Plaines, IL, USA). A minimum of 20 metaphases were analysed for each cell line.
Mutation analysis in Korean patients with T-cell acute lymphoblastic leukemia
Published in Pediatric Hematology and Oncology, 2020
Kyoung-Jin Park, In-Suk Kim, Eu Jeen Yang, Young Tak Lim, Su-Hee Cho
Tumor samples with at least 20% of blast cells were obtained from diagnostic bone marrow (BM) aspirates or peripheral blood stored in biobank of Pusan National University Yangsan Hospital from July 2016 to June 2018. In total, 10 unrelated patients were diagnosed as T-ALL based on morphology, immunohistochemistry, and immunophenotyping data according to World Health Organization criteria. We collected information about onset age, sex, BM study, and cytogenetic studies. The chromosome study was done in 9 patients using G-banding at a 400-band resolution. FISH study was done in 7 patients using XL CDKN2A Deletion Probe FISH and relevant detection probes (MetaSystems GmbH, Altlussheim, Germany). Recurrent genetic abnormalities were tested using HemaVision-28N Multiplex RT-PCR test (Hemavision, DNA Technology, Aarhus, Denmark). The study was approved by the Institutional Review Board of the Pusan National University Yangsan Hospital (05-2017-130). Informed consent was obtained from the patients.
A Review of the Role of Cytogenetics in the Diagnosis of Orbital Rhabdomyosarcoma
Published in Seminars in Ophthalmology, 2019
Paula Cortes Barrantes, Frederick A. Jakobiec, Thaddeus P. Dryja
The process of staining with Giemsa the digested chromosomes in metaphase is a technique that reveals dark and clear “banding” patterns specific for each chromosome. This technique, developed in the 1970s, was named G-banding due to the Giemsa stain used and became the routine method for cytogenetic analysis. In the 1980s, G-banding techniques performed on RMS disclosed a balanced translocation between chromosomes 2 and 13 in many cases of ARMS. This alteration was not present in cases of ERMS.11,12 In the early 1990s, another translocation was described, again involving chromosome 13 but exchanging genetic material with chromosome 1 instead of chromosome 213 Now it is known that at least 80% of ARMS tumors have one of the two translocations. One is t(2:13)(q35;q14), which juxtaposes the PAX3 gene on chromosome 2 with the FOX01 gene on chromosome 13. The other, t(1:13)(q36;q14), brings the PAX7 gene on chromosome 1 next to FOX.0114 Both translocations give rise to fusion genes that produce a “fusion protein” (also known as a chimeric protein). ARMS with these fusion proteins have been designated fusion-positive (ARMSp).