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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
Chromosomes examined from products of conception from pregnancy losses at various stages of gestation show an exceptionally high rate of chromosomal abnormalities. In fact, as many as 10% to 15% of early embryos have a chromosome abnormality, usually leading to a spontaneous pregnancy loss (27). Approximately 50% to 60% of spontaneous abortions are caused by a chromosome anomaly in the embryo or fetus (28). At the time of live birth, approximately 1 in 150 newborns is chromosomally abnormal. Thus, as stated by John Opitz, “it seems established that most of, ‘humanity’ dies before, rather than after birth, and that perhaps only a third survive from the earliest beginnings till [sic] birth…” (29). The most frequent abnormalities seen are autosomal trisomies (52%), especially trisomy 16 (15%), trisomy 13, 18, and 21. 45,X accounts for 18% of abnormalities and triploidy is found in 17% (30). There is a steady loss of these abnormal pregnancies throughout the first trimester. By 20 weeks, the incidence has fallen to 27 in 1000 or 2.7%, and by full term, the incidence is 6 in 1000 or 0.6% (28).
Genetics and metabolic disorders
Published in Jagdish M. Gupta, John Beveridge, MCQs in Paediatrics, 2020
Jagdish M. Gupta, John Beveridge
In individuals with a balanced Robertsonian translocation the chromosome number is 45 instead of the usual 46. In balanced reciprocal translocations chromosome number is 46. Six percent of couples who have had more than three miscarriages will be found to be carriers of a balanced chromosome rearrangements such as translocations; this is the underlying reason for pregnancy loss. Among families of infants with translocation Down syndrome, neither parent is shown to be a carrier approximately 50% of the time. The extra copy of chromosome 21 in non-disjunction trisomy 21 is more frequently of maternal than paternal origin, and the most frequent sex chromosome anomaly associated with early spontaneous abortion is 45,X (Turner syndrome).
Diseases of the Nervous System
Published in George Feuer, Felix A. de la Iglesia, Molecular Biochemistry of Human Disease, 2020
George Feuer, Felix A. de la Iglesia
This disease occupies the largest group among disorders of the central nervous system, causing mental retardation. Down’s disease is associated with a specific chromosome abnormality and is the most common of all chromosomal disorders in man. It is also known as mongolism or mongolian idiocy. The basis of Down’s disease is the aneuploidy; the cells of the affected persons usually show 47 chromosomes with trisomy for number 21. In such cases, one of the patient’s parents may be an asymptomatic carrier. Probably an aberration in the oogenesis rather than spermatogenesis is responsible for this disease. The parental chromosomes are normal and the abnormality originates from one of the meiotic cell divisions at conception or from the early cleavage of the zygote. Since increased age of the mother is associated with increased incidence of Down’s disease, the abnormality of maternal chromosomes is the probable cause of this disorder. In addition to regular Down’s disease with simple trisomy, possible translocation between this and another chromosome may occur, and in some cases, mosaicism of the trisomy and sex chromosome anomaly have also been shown. Current molecular biology studies are aimed at determining the gene responsible for the disease.
Trans Bodies, Trans Selves: A Resource for the Transgender Community by L. Erickson-Schroth
Published in Journal of Homosexuality, 2018
Rachel Levin’s commentary “Research on the Biology of Trans* Identity” gestures in this direction, raising the concept of cultural bias and asking readers if they would be concerned were a transgender gene identified and “excise[d] prior to birth” (p. 85). Not discussed is how biological determinism has been used to deny individuals autonomy. Joanne Meyerowitz (2002) details an open conflict throughout the 20th-century United States involving trans* people and doctors, scientists, judges, federal, state, and local government officials, the news media, and others over meanings of trans*, civil rights protections, access to resources, and punishments for nonnormative behaviors and thinking. In the 1980s, when sodomy was illegal in many U.S. states, research into hormones and fetal development to identify causes of homosexuality generated controversy.2 A recent mainstream radio call-in show discussed options for parents should a fetal genetic test reveal a sex chromosome anomaly. One course of action raised at the outset was abortion (Krasny, 2017). Tellingly, the history of eugenics features nowhere in the book.
Abnormal chromosomes identification using chromosomal microarray
Published in Journal of Obstetrics and Gynaecology, 2022
Yunfang Shi, Xiaozhou Li, Duan Ju, Yan Li, Xiuling Zhang, Ying Zhang
Other implications of this study for clinical practice included correct identification for recurrent risk in future pregnancies and other at-risk relatives. It is important to be alert to the possibility of a chromosome rearrangement in the family with a chromosome anomaly. The detection of the familial chromosomal translocation may direct the investigation of other family members and permit to plan future pregnancies (Gonzalez et al. 2018; Pasińska et al. 2018). In this study, three parents presented chromosomal abnormalities. One (case 3) was previously known, and the other two (case 1 and case 2) were detected after karyotype and CMA analysis. Other cases (cases 4–6) with normal parental karyotypes indicated that they were de novo cases.
Sleep quality and obstructive sleep apnoea and triple screen test results in pregnancy
Published in Journal of Obstetrics and Gynaecology, 2021
The chromosome anomaly ratio detected in amniocentesis cases in the literature is between 2% and 5.8% (Demirhan et al. 2011). In a study group that was composed of the most common prenatal diagnosis indications (such as high risk in the triple tests), the ratio of chromosome anomaly observed was 2.6% (Saatçi et al. 2007). Likewise, Biçer et al. (2007) detected chromosomal abnormalities in 2.7% of pregnant Turkish women with advanced maternal age and in 1.6% of patients with high risk in triple test. The risk of DS obtained in this study was slightly higher than the previous results. This difference can be explained by regional risks. Higher rates of advanced age pregnancies may have increased the risks of DS.