(a) Discrimination Based on Genetic Information.--It shall be an unlawful employment practice for an employer--
(1) to fail or refuse to hire, or to discharge, any employee, or otherwise to discriminate against any employee with respect to the compensation, terms, conditions, or privileges of employment of the employee, because of genetic information with respect to the employee; or
(2) to limit, segregate, or classify the employees of the employer in any way that would deprive or tend to deprive any employee of employment opportunities or otherwise adversely affect the status of the employee as an employee, because of genetic information with respect to the employee.
No.
In the US, it is currently illegal for genetic information to be used as a qualification for employment.
Your DNA never changes. Once it's on record it's on record. This isn't like prohibition where as long as you quit before the law comes into effect you are safe.
If there is ever a future time you can be punished for your DNA, the only people who can possibly be 'grandfathered' in are the ones who've avoided submitting their DNA in the first place. Everyone else can be punished after the fact.
I don't support the point of view of the GP but in all fairness, if we come to the society where DNA is used for widespread discrimination, it will probably be semi-voluntarily collected from the majority of the citizens anyway (e.g. want to have a driver's license? submit the DNA)
Your putting the onus on me to prove that it was explicitly the results of my test that caused me not to be hired.