Simple-

You have 2 people trapped inside of you (one set from mom, one set from dad)
Both of your parents had 2 people trapped inside of each of them (one from each of their parents)
Etc etc etc....

That means there was 4 possible traits for everything that makes you when your parents reproduced, but only 2 made it into your DNA- wich means that 2 have nothing to do with your genetic makeup and where lost (when it comes to your DNA structure). Just because one of your parents had a trait doesn't mean that you have it anywhere.

google eye color passive/recessive for a good example.


Selective breeding.
Passive and Recessive genes.

Prime example-
ALL dog breeds that we keep as pets are descended from wolves.
However, If I breed 2 rottweilers, the pups will be rottweilers, not poodles- even though both breeds ultimately came from the same ancestors- wich looked like neither 10,000 years ago.

And yes it is completely possible to ditch a trait from a parent.