Lethal genes (genes that result in the failure to develop a vital organ or metabolic pathway) are nearly always recessive. Animal breeders who discover a unique trait and selectively breed to increase the occurrence of that trait often encounter a noticeable increase in lethal genes. Why

Though these genes are recessive, it is still very much possible for the offspring to inherit this, and the lethal gene is no different.

Explanation:

Suppose this animal breeder picked a dog who appeared to be happy and healthy and paired with another healthy dog. One of these healthy dogs may have this recessive lethal gene, though they have not been affected by it, their offspring may be likely to.

the correct answer is 2 and 4