Irradiated mice given a stimulatory antigen fail to mount an adaptive immune response. A robust response can be restored by:

A bone marrow transplant (BMT)

Explanation:

An irradiated mouse would have immune hypocellularity or acellularity.  A BMT would replenish its immune system to mount a robust immune response.

the father in the first generation probably had the recessive colorblind trait in his x chromosome. if he and his wife both had the colorblind trait, even if she had 1 recessive and 1 dominant, then that trait would be passed on to their kids.

(since you didn't attach the family tree this is just an assumption)