Anyway, while talking to these kids about DNA I used a metaphor that I'm pretty (dorkily) proud of. 80% of the class were musicians. I told them that DNA is like the sheet music, or score, of a symphony. If you've ever seen the sheet music for a symphony, it can be as big as a doctoral thesis-length book. Likewise, the human genome, or complete set of DNA, is quite extensive. Are you following? So, each individual note in the score is like an individual base pair of DNA (you know, those letters A, T, C, or G). The order of the notes is important for the melody of the sheet music, while the order of the DNA base pairs is important to code for the genes of the genome. One mis-placed or lost note or notation in the sheet music can lead to an incorrect note, or perhaps a note that is cut short instead of held. Likewise, one mis-placed or lost DNA base pair can lead to an incorrect/mutated gene or perhaps silence the gene completely.
Still following? Each musician in the symphony can get a copy of the entire score, but each musician plays only their designated segment of the score, specialized for their respective instruments. Likewise, each cell in the body has an entire copy of the genome, but each cell expresses and uses only certain genes, specialized for the cell-types (ie. the gene for eye color is expressed only in the eye). Even more specifically, each musician plays their designated segments at certain times as directed by the conductor (and by the order of the notes). Gene expression can be turned on and off at certain times as directed by a variety of factors.
If the music notation in the sheet music is the genotype, or genetic code of an organism, then the sound of the music that is produced is the phenotype, or the physical outcome of gene expression (ie. blue eyes, blond hair, freckles, long toes, etc.). Humans share 99.9% of their genetic material, but that 0.1% of variation is sufficient to make us different at the genetic and physical levels (unless you have a twin. And we won't even get into nature vs. nurture today!). Along these lines, if two different sets of musicians play music from the exact same score, then there will be variation depending on how the musicians and the conductor interpret it.
OK, that is all I have for now, but I'm sure that there are more similarities out there. Music and science are so intertwined, and not just metaphorically! Here is an interesting article about "protein songs," for example.