You're listening to the inquiry on the BBC World Service with me, Helena Merriman.

Each week, one question, four expert witnesses, and an answer. When she was 29, Parol Samani sent a sample of her DNA to a company

to be tested. A few weeks later, she got an envelope through the door with the results. She opened it up and read the report. It wasn't good news.

She was told that she had a gene that often leads to breast cancer.

A few weeks later she met her doctor to talk through her options.

They decided to give her MRIs and mammograms every six months.

And that's how they caught her breast cancer, two years later.

She then had treatment and surgery, and she's now clear.

Genetic testing saved my life, she says.

She's now one of 12 million people who've had their genes tested.

People who are hoping to find out whether they might get cancer, heart disease or Parkinson's,

whether they descend from Neanderthals or Vikings, or if they've got any secret relatives they never knew about.

It's an industry that's booming all over the world, one which promises to reveal the story of us.

But there are those who question just how much our DNA actually reveals. So this week we're asking is gene testing

overrated. Part 1, the human genome.

The Human Genome.

You know, I've been curious about heredity for a long time and I suppose it really started to amplify when I became a father and I realized you know I'm passing down these genes that I inherited to new people.

It's a little frightening but also kind of fascinating.

That's Carl Zimmer, a science journalist who's just written a book all about genetics.

As I watched my daughters grow up, I've been trying to figure out, well, what did they inherit from me and from my wife? The answer to that lies in our genes.

So a gene is a stretch of DNA and it has information in it that your cells use to make molecules.

Is it a physical thing? What do they look like?

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