Now that you know the genetic alphabet (A),(C),(G),(T) and sometimes (U). And, now that you know how to spell using this alphabet three letters at a time. [called a codon] It is now time to put it all together into our DNA. So, drum roll please...
phosphate plus sugar plus nitrogenous base! Yes, that's right...phosphate + sugar + nitrogenous base. Say again...phosphate + sugar + base (nitrogenous) come together to form our DNA! So from now on, when you see the word DNA, you think, phosphate + sugar + base! Kind of rhymes "phosphate plus sugar plus base" makes us healthy, wealthy and wise. Well at least healthy, assuming all goes well at this biochemical level.
The phosphate atom is actually the little brother to the nitrogen atom so you can imagine that it is a strong fellow also. It combines with three oxygen atoms to form the backbone of the DNA helix. It then connects our sugar (called ribose) molecules, stringing them along the outside of the chain like Christmas tree lights. The ribose sugar then holds the nitrogenous base to the inside of the DNA chain. The nitrogenous base, our alphabet, flap their molecular structure toward the inside, holding out promise to its partner, asking a partner to come join me. Another nitrogenous base from the other side of the helix. A [adenine] will only combine with T [thymine], and C [cytosine] will only combine with G [guanine].
So there you have it...DNA... "deoxyribonucleic acid" = phosphate + sugar (deoxyribose)+ nucleic acid (nitrogenous base)!