This section made an interesting contrast between simple data that generates large and complex structures that require large and complex programs to handle them, and complex data which a complex but easy to use program helps a non-expert handle in some interesting, creative, flexible ways.
The case study on DNA illustrated how simple data (consisting of only four elements) can be combined into very large and complex structures (genes and chromosomes). You learned how such large and complex structures, when stored in databases, present certain computational problems. The difficulty of finding anything in such large databases where data may be very repetitive or partial, or its location not known means that huge computational effort is required, both to build the database in the first place, and then to use it effectively.
In contrast, the second case study examined how complex data, such as the graphical representation of a scene, can be made relatively easy to use by a non-expert. The case study showed how the flexibility of a computer and its ability to make and store multiple copies provides great scope for creativity.