There are one billion words in the book, which makes it longer than 5,000 volumes the size of this one, or as long as 800 Bibles. This is gigantic document, an immense book, a recipe of extravagant length, and it all fits inside the microscopic nucleus of assign cell that fits easily upon the head of a pin.

The idea of the genome as a book is not, strictly speaking, even a metaphor. It is literally true. A book is a pice of digital information, eritten in linear, one dimensional and one-directional form and defined by a code that transliterates a small alphabet of signs into a large lexicon of meanins through the order of their groupings.So is a genome. The only complication s that all English books read from left to right, and some from right to left, though never both at the same time.

Whereas English books are written in words of variable length using twenty-six letters, genomes are written entirely in three- letter words, using only four letters: A,C,G and T (which stand for adenine, cytosine, guanine and thymine). And instead of being written on flat pages, the are written on long chains of sugar and phosphate called DNA molecules to which the bases are act as side rungs. Each chromosome is one pair of (very) long DNA molecules.

The genome is very clever book, because in the right conditions can both photocopy itself and read itself. The photocopying is known as REPLICATION, and the reading as TRANSLATION. replicaion works because of an ingenious property of he four bases: A likes to pair with T, and G with C. S o a single strand of DNA can copy itself by assembling a complementary strand with Ts opposite all the As, As opposite all the Ts, Cs opposite all the Gs and Gs opposite all the Cs. In fact, usual state of DNA is the famous DOUBLE HELIX of the original strand and its complementary pair intertwined.

To make a copy of the complementary strand therefore brings back the original text. So the sequence ACGT become TGCA in the copy, which transcribe back to ACGT in the copy of the copy. This enables DNA to replicate indefinitely, yet still contain the same information.