Small parts of this genetic code can be responsible for large changes in cellular development and there are large parts of the code that we don't really know what it does.
This huge string of code is also a bit different to say reading a book, one word following the other until you get the the end - a linear progression. The genome consists of multiple layers of linear code that contain overlaps, loops and branches. And as much as I hate to use machine language to describe biology, it does seem that this genetic code is similar to computer language that has both linear and non-linear characteristics. There are encoded feedback loops - genes regulating genes that further regulate other genes, in real time in response to environmental conditions. It is a code that can rewrite portions of itself depending on various factors. (Others have compared DNA with a hard drive full of code and the RNA and protein molecules, and their interactions, as the active RAM of the cell.)
If it were a computer code we'd call it artificial intelligence of a very complex design rather than a random chance collection of computer characters. This multi-dimensional, dynamic and self-regulating genome is contained in a package smaller than any visible speck of dust. From this very tiny package comes the incredible capacity to direct cells into a multitude of forms and functions. The capacity of young neurons to migrate to just the right spot in the brain is amazing and the complexity of communication between cells is mind blowing. Sorry I realise these statements are not very satisfactory but I don't have the scope to go into what is amazing and mind blowing just now - but I'd love to look at these things a bit further down the track and amaze you and blow your mind!
The Darwinian perspective on all this complexity is that it must have started from a very simple genome and after a long (a very long) series of mutations (errors in replication) and natural selection (most adaptable mutations survive and reproduce). In other words, errors in the genome add some benefit to the organism (and presumably more complexity) and the organism with such mutations reproduce more than the non-mutated version. I don't think I need to tease this out too much because this is what we have all been taught in school biology. Remember the tree of life diagram with a single cell organism at the base of the tree and as the tree goes up and branches out the animals become more complex with man somewhere at the top? But is this the truth? Did a collection of free floating amino acids come together to form a primitive strand of DNA or RNA, and somehow get encapsulated into a membrane and somehow form the 'machinery' required to replicate and sustain it's form?...<<<Read More>>>...
