How is CF passed down?

I had a question thrown out to me yesterday on Facebook and I thought I'd share my answer here as well.

What if one parent has CF and the other parent is a carrier or isn't even a carrier, are your chances for having a CF child still the same? I'm so confused about this.

Since CF is a genetic disease it takes "bad genes" from both parents to have a baby with CF. As a CFer I have TWO copies of the bad gene. As a "carrier" you would only have ONE copy of the bad gene. Those who have no "bad genes" at all are neither carriers or CFers.

So, if two people with with TWO bad genes (both with CF) make a baby, the baby would virtually have a 100% chance of having CF since neither parent is able to pass down a "good gene".

If a CFer (TWO bad genes) makes a baby with a carrier (ONE bad gene and ONE good gene) the baby would have a 50% of getting TWO bad genes (the baby would have CF) and a 50% of getting ONE bad gene and ONE good gene (the baby would be a carrier)

If a CFer (TWO bad genes) makes a baby with a person who doesn't have CF and is not a carrier (TWO good genes) the baby would virtually have a 100% of getting ONE bad gene and ONE good gene therefore making the baby a carrier (ONE bad gene and ONE good gene).

If a carrier (ONE bad gene and ONE good gene) makes a baby with another carrier (ONE bad gene and ONE good gene) the baby would have a 25% chance of getting TWO bad genes (the baby would have CF) a 50% chance of getting ONE bad gene and ONE good gene (the baby would be a carrier) and a 25% of getting TWO good genes (the baby would not have CF and it would not be a carrier).

If two people who do not have CF and are not carriers make a baby, meaning they both have TWO good genes, then the baby would have a 0% chance of having CF.

Now this is obviously a very stripped down explanation but hopefully a simple enough one that is very easy to understand!