Final answer:
Treatments like gene therapy for genetic diseases such as SCID address the symptoms (phenotype) but often do not change the underlying genetic makeup (genotype). These treatments provide a 'phenotypic cure' by improving the observable characteristics or symptoms, while the genetic mutations are still present in the individual's DNA and can be inherited.
Step-by-step explanation:
When addressing genetic diseases like Severe Combined Immunodeficiency (SCID), treatments often focus on alleviating or correcting the phenotypic symptoms rather than changing the underlying genetic cause. This is due to the complexity of genetic disorders, which are caused by abnormalities within the genome impacting the normal function of proteins and cells. Current treatments, such as gene therapy, have the potential to insert normal genes into cells that harbor mutations, and while this can mitigate the symptoms or phenotype, it does not alter the patient's germ line and therefore is not a true genetic cure.
This phenomenon is described as a 'phenotypic cure' because the treatments can improve the phenotype—observable characteristics or symptoms of the disease—even though the genotype—individual's genetic makeup—remains unchanged. For single-gene disorders, where a defect in one specific gene can give rise to the disease, gene therapy holds promise. However, for most diseases influenced by multiple genes and environmental factors, predicting inheritance patterns, and addressing genetic disorders, becomes considerably more complex.
Treatments that target symptoms can be effective in improving quality of life and health outcomes. Nonetheless, they do not offer a permanent solution as the individual's DNA, which can be passed to the offspring if the gene is not in the germ line, contains the original mutation. Therefore, until treatments that can safely and effectively alter the germ line are developed and ethically approved, genetic diseases will generally only be treatable at the phenotypic level.