Manual: In a manual transmission, the problem is not so much the fluid degradation, but rather fluid contamination. This contamination occurs over time as the synchronizers, bearings and gears in the transmission wear out. The resulting metal particles then float around in the lubricant.
A lot of mental illnesses can have a genetic component, yes (eg. depression, bipolar disorder, anxiety, antisocial personality disorder, etc.).
This can cause a medical condition called a genetic disorder. You can inherit a gene mutation from one or both parents. A mutation can also happen during your lifetime. There are three types of genetic disorders: 1  Single-gene disorders, where a mutation affects one gene. 2  Sickle cell anemia is an example.