Bilineal Inheritance and Polygenic Complex Disorders

In the realm of genetics, understanding the complexity of how traits and disorders are passed down through generations is pivotal. Among these complexities lies the concept of bilineal inheritance, which refers to the transmission of genetic traits or disorders from both parents to their offspring. This contrasts with unilineal inheritance, where traits are passed down from only one parent. Bilineal inheritance plays a significant role in the development of polygenic complex disorders, which are conditions influenced by multiple genes and often environmental factors. These disorders are characterized by their multifaceted genetic architecture, making their study both challenging and crucial for advancements in medical genetics.

Evidence of Bilineal Inheritance and Polygenic Complex Disorders
Polygenic Nature of Psychiatric Disorders: Research highlights that psychiatric disorders, including childhood and adult onset psychiatric conditions, exhibit a polygenic nature. This means these disorders result from the influence of multiple genetic variants, including both common and rare variants in the population. The study of polygenic risk scoring and heritability estimation from common SNPs has shed light on the genetic architecture of psychiatric disorders, emphasizing the polygenic basis of these conditions (Wray et al., 2014).

Genetic Prediction of Complex Traits: The development of statistical methods for genetic prediction of complex traits, such as disease susceptibility, has been crucial. These methods, which include the construction of polygenic scores (PGS), demonstrate the substantial polygenic influence on complex traits. Through the aggregation of information across multiple genetic variants, PGS can predict a broad spectrum of diseases, underscoring the polygenic nature of these conditions (Ma & Zhou, 2021).

Heterogeneity and Polygenicity in Psychiatric Disorders: The genome-wide association studies (GWAS) on psychiatric disorders reveal a complex polygenic architecture linking mental and physical health phenotypes. The heterogeneity and polygenicity of these disorders suggest that multiple layers of trait complexity and genetic risks contribute to the discovery of risk loci per disorder or across multiple disorders. This understanding is critical for developing treatment strategies based on genetic findings (Wendt et al., 2020).

Polygenic Influences on Heart Failure and Stroke: The review of genetic polymorphisms in heart failure and stroke illustrates the polygenic contributions to these conditions. Studies on polymorphisms of various systems, including the renin-angiotensin-aldosterone system (RAAS) and the sympathetic system, highlight a modifying role for these polymorphisms in the development of heart failure and stroke, supporting the notion of polygenic and possibly oligogenic inheritance patterns (Bleumink et al., 2004; Bersano et al., 2008).

Conclusion
The concept of bilineal inheritance and its role in polygenic complex disorders underscores the intricate nature of genetic transmission and the multifactorial basis of these conditions. The evidence from research in psychiatric disorders, heart failure, stroke, and other complex traits emphasizes the importance of understanding the polygenic architecture of diseases. This knowledge is crucial for advancing genetic predictions, developing personalized medicine, and ultimately improving patient care.

References:

Wray, N., Lee, S., Mehta, D., Vinkhuyzen, A., Dudbridge, F., & Middeldorp, C. (2014). Research review: Polygenic methods and their application to psychiatric traits.. Journal of child psychology and psychiatry, and allied disciplines, 55 10, 1068-87 . https://doi.org/10.1111/jcpp.12295.
Ma, Y., & Zhou, X. (2021). Genetic prediction of complex traits with polygenic scores: a statistical review.. Trends in genetics : TIG. https://doi.org/10.1016/j.tig.2021.06.004.
Wendt, F., Pathak, G., Tylee, D., Goswami, A., & Polimanti, R. (2020). Heterogeneity and Polygenicity in Psychiatric Disorders: A Genome-Wide Perspective. Chronic Stress, 4. https://doi.org/10.1177/2470547020924844.
Wendt, F., Pathak, G., Tylee, D., Goswami, A., & Polimanti, R. (2020). Heterogeneity and Polygenicity in Psychiatric Disorders: A Genome-Wide Perspective. Chronic Stress, 4. https://doi.org/10.1177/2470547020924844.
Bleumink, G., Schut, A., Sturkenboom, M., Deckers, J., Duijn, C., & Stricker, B. (2004). Genetic polymorphisms and heart failure. Genetics in Medicine, 6, 465-474. https://doi.org/10.1097/01.GIM.0000144061.70494.95.
Bersano, A., Ballabio, E., Bresolin, N., & Candelise, L. (2008). Genetic polymorphisms for the study of multifactorial stroke. Human mutation, 29(6), 776-795.