China
Africa
Explore chapters and articles related to this topic
Genomics and Hearing Loss: Toward a New Standard of Care?
Published in Stavros Hatzopoulos, Andrea Ciorba, Mark Krumm, Advances in Audiology and Hearing Science, 2020
The autosomal dominant inheritance refers to a trait or disorder in which the associated phenotype can be expressed in individuals who have only one copy of a pathogenic variant at a particular locus. The individual is said to be heterozygous for the trait. This pattern specifically refers to a gene located on one of the 22 pairs of autosomes, that is, a nonsex chromosome. For a given type of hearing loss, if individuals in each generation are affected and both males and females are equally affected, the pattern of inheritance is probably autosomal dominant. Also, all affected individuals will have at least one parent who carries the disease allele unless a new mutation has occurred.
Clinical genetics
Published in C. Simon Herrington, Muir's Textbook of Pathology, 2020
Autosomal dominant inheritance (Figure 5.14A) is a pattern of inheritance in which one copy of a mutant allele is sufficient to cause disease: an affected individual possesses one copy of the mutant allele and one copy of a normal allele. Individuals who have an autosomal dominant disease have a one-in-two, or 50%, chance of passing the mutation to all their offspring.
The eye
Published in Angus Clarke, Alex Murray, Julian Sampson, Harper's Practical Genetic Counselling, 2019
A remarkable number of X-linked disorders affecting the eye are known, and these are listed separately (Table 19.1), because they produce special problems in genetic counselling. The carrier state can be recognised in a number of these, and they provide direct evidence for mosaicism due to X-chromosome inactivation in the female. Patchy morphological changes can be seen in a number of these carriers, which allow diagnosis of the carrier state without recourse to investigations. However, molecular genetic analysis can now very often provide accurate tests based on the direct detection of mutations, especially for this X-linked group, but also for some autosomal disorders.
Reflex single-gene non-invasive prenatal testing is associated with markedly better detection of fetuses affected with single-gene recessive disorders at lower cost
Published in Journal of Medical Economics, 2022
Shan Riku, Herman Hedriana, Jacqueline A. Carozza, Jennifer Hoskovec
Autosomal recessive disorders represent a large disease burden worldwide1. Manifestation of autosomal recessive disorders in the first 25 years of life is estimated to be 1.7 in 1,0002 and can be considerably higher in certain populations3. Carrier screening is a genetic testing methodology that aims to identify individuals or couples who carry one variant allele within a gene and are at risk of having offspring with the associated genetic disorder4. The American College of Obstetricians and Gynecologists (ACOG) recommends all patients who are considering pregnancy or currently pregnant be carrier screened for cystic fibrosis (CF), spinal muscular atrophy (SMA), and hemoglobinopathies4. Most patients are screened after they become pregnant, with one 2019 study reported that 436 out of 462 patients (94.4%) undergoing carrier screening were screened prenatally5.
Torpedo-like lesions in the ocular fundi of Gardner syndrome: hiding in plain view
Published in Ophthalmic Genetics, 2021
Kirk Packo, Morton F. Goldberg
The APC gene (Adenomatous Polyposis Coli), located on chromosome 5, is noteworthy for its approximately 700 mutations spread along its length like a string of pearls. Their varied clinical abnormalities include the following: supernumerary teeth, cranial osteomas, epidermal cysts, intestinal polyposis, brain and other tumors (both benign and malignant), as well as a variety of pigmentary abnormalities in the fundus. Each of these abnormalities in Gardner syndrome/FAP can be inherited singly or in combination, or, importantly, not at all. Variability in appearance is typical, depending on how many (and which) exons harbor the different mutations. For example, Olschwang et al. (48) showed that varied extracolonic manifestations of the FAP syndrome are correlated with specific mutations in the APC gene; and, as noted by Alberge et al. (47), the RPE lesions in FAP are due to varied APC mutations between codons 541 and 1309. Additionally, the number of colonic polyps is correlated with different but specific mutations in the APC gene. When the number of polyps is small, the different clinical phenotype is separately named “Attenuated FAP”. In summary, the clinical appearance of affected individuals depends on the highly varied pleiotropic expressions of the abnormal gene in individual patients. Such varied clinical expressions are frequently observed in autosomal dominant diseases.
Preparing for the Next Generation of Ethical Challenges Concerning Heritable Human Genome Editing
Published in The American Journal of Bioethics, 2021
Yet, these situations pose key questions that have not yet been addressed. If both parents are homozygous for an autosomal recessive condition, they would both have the disease. But if they did so, and had reached reproductive age, and were able to have children, the disease would, therefore, be relatively treatable and not extremely severe and lethal to the degree that HHGE would necessarily be justified, given the risks involved. With new treatments for CF and bone marrow transplants for blood disorders, for instance, such homozygous patients are in fact able to reach reproductive age. But such treatment effectiveness also reduces the potential needs for HHGE. The Report, however, does not mention treatability. Early Onset Alzheimer’s would not affect future children for decades, by which time effective treatments may exist. Homozygous individuals for an autosomal dominant condition (e.g., HD, neurofibromatosis, or Marfan syndrome) rarely reach reproductive age.