Final answer:
Prader-Willi syndrome (PWS) and autism spectrum disorder (ASD) are complex neurological developmental disorders with known genetic components, but the detailed mechanisms connecting genetic changes to their wide array of symptoms are not fully understood.
Step-by-step explanation:
Although the genetics behind Prader-Willi syndrome (PWS) are known, the exact mechanisms linking these genetic alterations to the wide array of symptoms, including intellectual disability, seizures, behavioral issues, and psychiatric disorders, remain elusive. Children with PWS have a loss of function of genes on chromosome 15, which are not typically inherited but occur during egg or sperm formation, or embryonic development. Early signs of PWS, such as lack of muscle tone and poor sucking behavior, can be noticed from birth to 2 years of age. Developmental delays are common between ages 6 and 12, leading to excessive eating and cognitive deficits associated with PWS. The condition may involve hypothalamic abnormalities that also affect the regulation of sexual behavior and failure to reach sexual maturity.
Similarly, while some disorders like Fragile X and Rett's Syndrome have clearly identifiable genetic causes, other conditions such as autism spectrum disorder (ASD) involve a complex interplay of multiple gene variants and mutations. These genetic factors result in brain developmental differences from normal patterns, potentially due to disruptions in processes like synaptic pruning. Like PWS, the specific causal links between the genetic changes and the full spectrum of symptoms in ASD are not yet fully understood, underscoring the complexity of neurological developmental disorders.
Environmental factors and age-related errors in mitotic cells also contribute to the development of these disorders, emphasizing the multifaceted nature of their onset and progression.