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Aneuploidy in Human Oocytes and Preimplantation Embryos
Published in Carlos Simón, Carmen Rubio, Handbook of Genetic Diagnostic Technologies in Reproductive Medicine, 2022
In human oocytes, not all chromosomes are created equal with regards to their risk of aneuploidy and their maternal age-related curves (19,24–26,45). This includes the preponderance of aneuploidies for specific chromosomes, especially the largest chromosomes (1 to 5), which missegregate in young teenagers (19), whereas the two smallest chromosomes 21 and 22, but also 15 and 16, tend to be error-prone in women of advanced maternal age. There are also some chromosomes, such as chromosome 13, that initially show a high incidence in young teenagers, then improve, before showing elevated aneuploidy in women of advanced maternal age. However, in general, size correlates negatively with age-related aneuploidy (26).
Practice exam 4: Answers
Published in Euan Kevelighan, Jeremy Gasson, Makiya Ashraf, Get Through MRCOG Part 2: Short Answer Questions, 2020
Euan Kevelighan, Jeremy Gasson, Makiya Ashraf
BRCA1 chromosome 17, BRCA2 chromosome 13. Repair damaged DNA. Fixed mutations in other genes.
Oncogenes and Cancer
Published in Pimentel Enrique, Oncogenes, 2020
A deletion of human chromosome 13, region 13ql4, is observed microscopically in less than 5% of children with retinoblastoma,343 although it is conceivable that the deletion may be present in a higher proportion of retinoblastoma patients because it can occur at a submicroscopical level, as can be determined by DNA hybridization methods.344,345 However, no proto-oncogenes have been assigned to human chromosome 13. Hypothetically, the deleted region on this chromosome would contain not an oncogene but, on the contrary, a tumor-suppressing gene.344 A phenomenon of gene deletion associated with duplication and homozygosity of nondeleted alleles, similar to that described in Wilms’ tumor,336,337 also occurs in the tumor cells of some cases of retinoblastoma.346,247 The chromosome region 13ql4 contains, in addition to the putative retinoblastoma-suppressing gene, the locus for the enzyme esterase D (ESD), and there is evidence that somatic inactivation of genes corresponding to both loci are common in retinoblastoma tumor cells.
Complex translocation leading to13q interstitial deletion in a Moroccan child with retinoblastoma and intellectual disability
Published in Ophthalmic Genetics, 2022
Zhour EL Amrani, Siham Chafai Elalaoui, Wafae Jdioui, Aziza Sbiti, Ilham Ratbi, Thomas Liehr, Abdelaziz Sefiani, Abdelhafid Natiq
A review of the literature of similar patient reports with RB1-gene deletion, chromosomal rearrangements, and other symptoms than isolated RB (mainly developmental delay and facial dysmorphism) is summarized in Table 2. Chromosome 13 being involved in rearrangements with autosomes (9 cases) and such involving X-chromosome and chromosome 13 are reported (6 cases). Common feature for those cases is an early age of RB-formation, independent of gender, between 5 months and 10 years. Majority of chromosomal abnormalities were sporadic (12 cases) and only 3/15 cases inherited. Most interesting family here is that reported by Strong et al. with affected members over four generations, being transmitted by eight unaffected individuals, which led to the identification of the RB1 gene (7).
The performance of grey zone in common foetal aneuploidy screening by semiconductor sequencing
Published in Journal of Obstetrics and Gynaecology, 2022
Chunhua Zhang, Quanze He, Longwei Qiao, Hong Li, Ting Wang
Z score distribution of 274 samples with chromosome 21, 18, or 13 in the grey zone and their karyotyping analysis results can be seen in Tables 2 and 3. In the first run of cfDNA test, 184 samples had their z score of chromosome 21 in the grey zone, 104 samples had z score of 2.58–3 and 40 samples had z score >3. After the second run of cfDNA test, 176 samples present z score of −2.58–2.58, categorised as screening negative aneuploidy 21, four ‘gray’ samples were classified as screening positive aneuploidy 21, and one of these four samples was then confirmed as affected T21 by the foetal karyotyping. Fifty-four samples with chromosome 18 in the grey zone were all classified as negative after the second run of NIPT. Of thirty-one samples with z score of chromosome 13 in the grey zone, 26 cases were categorised as screening negative aneuploidy 13 after the second run of NIPT, and one of the five screening positive samples was confirmed as affected T13 by foetal karyotyping.
MYCN amplification levels in primary retinoblastoma tumors analyzed by Multiple Ligation-dependent Probe Amplification
Published in Ophthalmic Genetics, 2021
Elizabeth A. Price, Roopal Patel, Irene Scheimberg, Esin Kotiloglu Karaa, Mandeep S. Sagoo, M. Ashwin Reddy, Zerrin Onadim
Peripheral blood was collected into EDTA tubes whilst fresh tumor was harvested by pathologists and frozen for storage immediately after enucleation. DNA was extracted as previously described (4,11). RB1 screening covered all 27 exons plus 50 bp upstream and 30 bp downstream to cover associated splice sites, as well as the promoter. Conformation analysis of transitions/transversions and small insertions/deletions was performed by single stranded conformational polymorphism and heteroduplex analysis (GE Biotech ALFexpress), and/or high resolution melt analysis (Corbett RotorGene 6000). Samples giving abnormal traces were reamplified for Sanger sequencing. Polymorphic markers within and around RB1 on chromosome 13 were used to determine tumor LOH. Large exonic deletions were detected by in-house Quantitative Fluorescent PCR (QF-PCR) and Multiplex Ligation-dependent Probe Amplification (SALSA MLPA RB1 probe mix P047, MRC-Holland) (11). Methylation specific PCR (MS-PCR) of bisulphite-modified DNA was performed to detect promoter hypermethylation (4). Around 97% of expected pathogenic variants (including MYCNA cases) were routinely detected over the last fifteen years (April 2005-March 2020).