what makes DNA store info in discrete "bits"? is each "bit" like the code for a protein?
In the case of DNA you can take every base as a discrete unit. The word discrete means that there are a finite (countable) number of possibilities.
Contrast, if you will, a CD with an LP. In a CD the music is encoded in sequence of zeros and ones. there are only two possibilities for every unit of information. that`s a countable number of possibilities, which makes the information content of CD`s discrete or Digital.
LP`s(Venyl), on the other hand, have the music encoded into microscopic grooves that cannot be broken down into units with finite (countable) possibilities. That makes them analag.
DNA, like CD`s, have their information encoded in discrete form. Every base has 4 possibilities -- a,c,t,g -- which is countable (Digital)
I hope that helps