What is the difference between a prezygotic barrier and a postzygotic barrier ?

Reproductive isolation is a mechanism that keeps species from mating with others. Prezygotic isolation prevents the fertilization of eggs while postzygotic isolation prevents the formation of fertile offspring. ... Postzygotic mechanisms include hybrid inviability, hybrid sterility and hybrid "breakdown." i hope this helped you.

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)

carbon

explanation: