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The Scientific Basis of Medicine
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Chris O'Callaghan, Rachel Allen
Monogenic diseases are the simplest genetic disorders to study as they tend to follow Mendelian genetics. Dominant and recessive diseases have characteristic patterns of inheritance (Figure 2.10). Dominant traits require only one defective copy to generate a disease phenotype. In contrast, recessive disorders are only visible when both copies of a gene are mutated. Recessive disorders often result from a loss in biological activity for the relevant protein. Sex linkage alters Mendelian genetics, as males carry only one copy of the X chromosome; recessive mutations carried on this chromosome behave as if dominant in men, while heterozygous females act as asymptomatic ‘carriers’. Polygenic disorders have a known genetic component (such as type 1 diabetes) but involve many genes and often environmental factors too (Table 2.1). In such cases, disease results from a combination of multiple polymorphisms, acting in concert with external factors. The risk of disease conveyed by each individual genetic variant in a polygenic disorder is relatively low and much lower than that conveyed by a genetic mutation in a monogenic disorder.
Genomic Informatics in the Healthcare System
Published in Salvatore Volpe, Health Informatics, 2022
It is challenging to understand the phenotype-genotype correlation and phenotypic variability of individuals with a specific genetic variant. Many alternative explanations for differing phenotypes among cases with the same genetic variant have been proposed. One consideration is the presence of another genetic variant that affects disease presentation. A true digenic disorder requires the inheritance of a distinct heterozygous mutation in two genes that, when inherited separately, do not cause a phenotype. The broader term of epistasis refers to possible interactions between genes. Determining genetic epistasis is complex and requires an appropriate pedigree, which includes more than one gene mutated in a single pedigree, a range of genetic permutations, and at least one member with wild type (WT) alleles in both genes.
The Meta-Analysis of Genetic Studies
Published in Christopher H. Schmid, Theo Stijnen, Ian R. White, Handbook of Meta-Analysis, 2020
Cosetta Minelli, John Thompson
A second issue is whether or not to include studies from different regions of the world: for example, is it appropriate to include a study from China in a GWAS meta-analysis that is predominantly based on people of European origin? The frequencies of most genetic variants show wide variation between ethnicities (Gibbs et al., 2003) but this is not the main concern. The key question is whether it is reasonable to assume that the effect of the genetic variant on the outcome will be the same in all populations (Marigorta and Navarro, 2013). Shared biology would suggest that the same genes will be important in all populations, but gene-environment interactions (Hunter, 2005) might introduce substantial heterogeneity in average effect size. Gene-gene interactions might also introduce heterogeneity when allele frequencies differ across populations (Battle et al., 2007).
Nurtured Genetics: Prenatal Testing and the Anchoring of Genetic Expectancies
Published in The American Journal of Bioethics, 2023
Rémy Furrer, Shai Carmi, Todd Lencz, Gabriel Lázaro-Muñoz
Due to advances in personalized genomics, it has become possible to quantify genetic variance and use it as an individual source of information. Polygenic Scores (PGS) are probabilistic scores that can provide information about an individual’s genetic likelihood of developing any (conceivably measurable) phenotypic trait. (i.e., extraversion, intelligence, height…etc.). Not only is genetic variance quantifiable and accessible as a source of information, but it can also precede most sources of environmental variance through prenatal testing. That is, parents can receive probabilistic genetic scores as the very first piece of evaluative information about their child. This genetic information will precede any (observable) environmental influences on their child’s development, and it is upon these initial probabilistic genetic estimates that they will create expectancies as to who their child will become and how they will behave. The concern is that polygenic scores—which only account for a relatively small portion of individual behavioral variability (see Plomin and Von Stumm 2022 for recent PGS estimates)—will lead parents to over-value genetic information over subsequent environmental information in forming an initial impression of their child.
Gene-environment Interaction in Spherical Equivalent and Myopia: An Evidence-based Review
Published in Ophthalmic Epidemiology, 2022
Xiyan Zhang, Qiao Fan, Fengyun Zhang, Gang Liang, Chen-Wei Pan
Genetic vulnerability is a significant risk factor for myopia. In the past, family or twin designs were often used to explain the genetic variance in a trait.5 Recently scholars have tried to determine genetic variance, focusing on single-nucleotide polymorphisms by genome-wide association studies.6,7 Almost 200 genetic loci have genetic effects on myopia/refractive error, but the individual genetic effect is moderate or small.8–11 Therefore, it is suggested that ‘Expanding extensive and depth genetic studies using substantial data analytics, and focusing on particular phenotypic subgroups and high familial aggression occurrence.’ In most twin studies used for assessing genetic and environmental contributions to myopia, they indicated that genes explained more than 50% of the spherical equivalent variance.12–17
Moral foundations in chronotypes: morningness predicts conservative morality
Published in Chronobiology International, 2021
Adrianna Zielińska, Maciej Stolarski, Konrad S. Jankowski
Overall, the present findings form a coherent picture in which people with morning chronotype are more conscientious and, therefore, manifest more conservative morality. Conscientiousness, one of the strongest correlates of morningness (Hogben et al. 2007), manifests in a preference for order, routine, and compliance. Similar principles underpin the right-wing worldview, which is based on traditional, conservative values and maintaining the status quo. It is worth mentioning here that we avoid formulating any ultimate claims regarding the causal mechanisms underpinning the association between morning preference and conscientiousness. Following Hogben et al. (2007), we rather believe that the two traits presumably share a significant portion of common genetic variance, which manifests in phenotypic correlations between these features. The interpretation seems to be supported by a recent longitudinal study by Stolarski et al. (2021), who showed a marked cross-sectional covariance between morningness and conscientiousness but no evidence for any causal (i.e., cross-lagged) effect between these dimensions. Based on the present results, the same part of variance may lead to a more conservative morality; however, in this case, longitudinal and/or behavioral genetic studies would be necessary to ultimately determine causality of the obtained association. Nonetheless, it seems plausible that both morningness and conservatism could to some extent stem from a generalized tendency to conform to social norms (the former – to the social clock, the latter – to well-established traditional values) contained in Conscientiousness.