In the case of genetic disorders, the root cause is your parents giving you bad genes, and your parents are outside your body.
This is too absolute: many genetic disorders are caused by de novo mutations that are not inherited from either parent.
Full reasoning
This statement treats genetic disorders as if they necessarily come from parents passing down a harmful variant. That is not correct.
Authoritative genetics references explain that some disease-causing variants are de novo (new) variants: they are found in the affected child but not in either parent. MedlinePlus Genetics states that de novo variants are one explanation for genetic disorders in which a child has the variant in every cell, "but the parents do not, and there is no family history of the disorder." It also explains that such variants can arise in a parent's egg or sperm cell or in the fertilized egg shortly after conception.
NIH's NICHD gives Rett syndrome as a concrete example: most cases are caused by a mutation in a single gene, and "such random mutations are usually not inherited or passed from one generation to the next."
So while some genetic disorders are inherited from parents, it is false to say that in genetic disorders the root cause is your parents giving you bad genes. Many genetic disorders arise from new mutations instead.
2 sources
- What is a gene variant and how do variants occur?: MedlinePlus Genetics
Some genetic changes are described as new (de novo) variants ... De novo variants are one explanation for genetic disorders in which an affected child has a variant in every cell in the body, but the parents do not, and there is no family history of the disorder.
- What causes Rett syndrome? | NICHD
Such random mutations are usually not inherited or passed from one generation to the next.