Can your DNA fit in a gigabyte?

How much information can you hold? Almost every cell in your body has a text written with just four letters. About three billion of them. Put into a computer, it fits in less than a gigabyte. And this text does something no book can: it copies itself.

This episode asks: what is something that copies itself? 1952. In London, Franklin’s lab captures an X-ray image of DNA: Photo 51. A blurry X that, to those who can read it, screams one word: helix. 1953.

In Cambridge, Watson and Crick use Franklin’s data to build a model. Two twisted strands, letters pairing up. A with T. C with G. Always.

Never any other way. Rosalind Franklin died in 1958, aged 37. The DNA Nobel came four years later. And Nobel Prizes don't go to the dead. They modestly note: pairing may let genetic material copy itself.

Unzip it halfway, and each half builds the missing half. One ladder becomes two. Life is a text that can make a copy of itself. But what does that text say? 1961.

Nirenberg and Matthaei make RNA, DNA's cousin, where T becomes U. Just one letter, repeated. U, U, U, U. They put it in a cell broth, and get a protein made of one building block. They put it in a cell broth.

A protein made of a single building block comes out. The code has 64 three-letter words for about 20 building blocks. Life writes in three-letter words. What if this applies beyond genes? 1976.

Biologist Richard Dawkins coins a word in The Selfish Gene: meme. From Greek: “something imitated.” A melody, a catchphrase, a fashion, a way to make a pot. Ideas that leap from mind to mind, copying and competing like genes. Remember the first video?

Meme is a biologist's term. There he is. An idea can be contagious too. But no copy is perfect.

Sometimes a letter gets swapped. That's mutation. Most of the time, it makes no difference. Sometimes it ruins things. And, very rarely,

it helps. That's where life's variety comes from. Remember multiplication tables? There, a copying error was a disaster. In life, it's raw material.

2003. 13 years, 20 centers, six countries: the Human Genome Project spells the book. Today, reading a whole genome takes days. Not years. Think what life already knew.

Before any engineer, it solved the three things that make information last. Write in a code. Copy carefully. Keep two strands, mirror images, to correct mistakes. Redundancy again.

The Congo drum would approve. So, what is something that copies itself? A recipe carrying instructions to make its own copy. Gene. Meme.

Life is information that learned to copy itself. But when everything copies, there's too much. Too much news.

Too much text. Too much data. And in the middle of this flood, how does anything make sense again? This story is told by XMACNA.

We live its newest chapter: Digital Employees put this intelligence to work, under your control. Follow XMACNA for the next episode. The Information. Episode ten: The Code of Life.

Inspired by The Information, by James Gleick. Read the book.