Читать книгу Lifespan Development - Tara L. Kuther - Страница 113

The principles of dominant–recessive and incomplete dominance inheritance can account for over 1,000 human traits (McKusick, 2007). However, a few traits are determined by a process known as genomic imprinting. Genomic imprinting refers to the instance in which the expression of a gene is determined by whether it is inherited from the mother or the father (Kelly & Spencer, 2017; National Library of Medicine, 2017). For example, consider two conditions that illustrate genomic imprinting: Prader-Willi syndrome and Angelman syndrome. Both syndromes are caused by an abnormality in the 15th chromosome (Kalsner & Chamberlain, 2015). As shown in Figure 2.5, if the abnormality is acquired by the father (illustrated in black), the individual—whether a daughter or son—will develop Prader-Willi syndrome, a set of specific physical and behavioral characteristics including obesity, insatiable hunger, short stature, motor slowness, and mild to moderate intellectual impairment (Butler, Manzardo, Heinemann, Loker, & Loker, 2016). If the abnormal chromosome 15 arises from the mother (shown in red), the individual—again, whether it is a daughter or a son—will develop Angelman syndrome, characterized by hyperactivity, thin body frame, seizures, disturbances in gait, and severe learning disabilities, including severe problems with speech (Buiting, Williams, & Horsthemke, 2016). Prader-Willi and Angelman syndromes are rare, occurring on average in 1 in 12,000 to 20,000 persons (Kalsner & Chamberlain, 2015; Spruyt, Braam, & Curfs, 2018). Patterns of genetic inheritance can be complex, yet they follow predictable principles. For a summary of patterns of genetic inheritance, refer to Table 2.2.

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Figure 2.5 Genomic Imprinting

Source: C. Cristofre Martin, 1998.