As mentioned before, the instructions on how to build a protein are stored in a
blueprint, the gene. Genes are encoded on nature's universal storage system, a
-molecule called "desoxyribonucleic acid", or in short DNA.
+molecule called "desoxyribonucleic acid", or in short DNA. DNA was discovered
+in 1869 by Friedrich Miescher at the University of Tübingen, in this lab in the
+basement of the Castle of Tübingen.
+
+DNA consists of a linear backbone (the desoxyribose). This backbone carries the
+actual information-containing molecules, the nucleobases or bases in short.
+There are four different bases in DNA, adenine, thymine, guanine and cytosine,
+abbreviated as A, T, G, and C respectively. DNA turns out to be an efficient
+and robust storage for information. This is partly because in nature a DNA
+strand always comes together with a backup copy, the so-called complement
+strand. The complement strand is an inverse copy of the original strand, with
+adenine being complemented by thymine and guanine being complemented by
+cytosine. Even if only one of the strands is present, this can be used to
+recover the complete set of information. The two DNA strands usually wind
+arournd each other in the twisted double helix you usually see when people talk
+about DNA.
+
+In bioinformatics, you usually only store one strand because calculating the
+complement strand is trivial. So all you need to store is a (potentially pretty
+long) sequence of As, Ts, Gs and Cs.
(Quip about a graded test at the end of the talk)