Is an asteroid impact a short term or long term change?

It depends the  size of the Asteroid.

Explanation:

If the Asteroid is rather bigger then most common ones then the affects could be long term. It also depends on the area it hits in. Most of the time they are rather short like 2-3 year repair

this is true, assuming that the allele is completely recessive and incomplete dominance is not a factor.

i think its y= -4x-14