The riot of opinions following Angelina Jolie’s revelation has a fair portion of us more inflamed than informed.

First, the customary two-minute science class.

Back to biology

The DNA of all human beings is 99.9 per cent similar. This means that beside environmental factors, this 0.1 per cent variation is what accounts for the differences between you and me.

One especially important difference is our susceptibility to diseases like cancer. Scientists have found that if specific genes (functional parts of our DNA) exist in mutated forms in an individual, that individual carries a much higher risk of getting the disease.

BRCA1 and BRCA2 are two such genes. In its normal version, both are responsible for preventing tumours. People (chiefly women) carrying mutations on either of these genes have been shown to be much more prone to getting breast and ovarian cancer.

It may be useful to note that when certain news articles make statements like “BRCA gene is rare”, what they mean to say is that the harmful BRCA mutations are rare. The BRCA gene itself is present in all of us.

How did Angelina Jolie come into the picture?

Jolie’s mother died of cancer at 56. Because of the family history, Jolie chose to undergo a genetic test. She found out that she had inherited a risky mutation in her BRCA1 gene.

This meant that Jolie had a higher-than-usual chance of developing the cancer. Instead of just hoping for the best and keeping a cautionary eye on her health, Jolie chose a more radical path: preventive double mastectomy.

This means she had the at-risk breast tissue removed from both her breasts. This was followed by reconstructive breast-implant surgeries. This drastically reduces Jolie’s chances of contracting the disease.

She spoke of her ordeal in a New York Times op-ed last week. This op-ed made a lot of noise.

Why are people mad?

People are mad because of a number of reasons. That Jolie, a much-admired actress and activist, may be inducing paranoia in women is the milder of the reasons for the uproar.

The harshest, scandalous and most confusing noise is coming from another corner. This corner is suspicious of the timing of Jolie’s announcement with respect to an ongoing U.S. Supreme Court case.

What case?

AMP (Association for Molecular Pathology) versus Myriad Genetics is the name of the case.

Myriad is a Utah-based company that holds the patent for the BRCA genes. This is because they were the ones who in 1994 identified risky mutations on the genes (though the existence of a breast cancer gene was already suggested by Mary-Claire King in 1990).

This means that if anyone wants to get tested for a BRCA mutation, they must use Myriad’s testing kit which costs US $3,000. The actual cost of testing is only about $200.

Much of the scientific fraternity and general population are opposed to the idea of one company restricting their access to cheap healthcare. Hence, the case.

The outcome of the case is expected in June. It may be a deciding factor in the bigger question of whether human genes can be owned.

What does Jolie’s op-ed have to do with this?

On the day the Op-ed was published, Myriad’s share price reportedly jumped to a three-year high. Loud whispers are beginning to be heard on the lines of “Angelina Jolie part of a clever corporate scheme to protect billions in BRCA gene patents, influence Supreme Court decision.”

At least, that’s what an article on NaturalNews.com, a non-profit health portal that promotes “positive changes in health and informed skepticism”, screams out.

You may be interested to know that the same article also carries a statement that says “eating raw cruciferous vegetables” can “suppress the BRCA1 gene” and “prevent breast cancer”. This can’t be right because BRCA1 is a tumour-suppressor gene. That means BRCA1 suppresses tumours – which is a good thing. So why would we want to suppress a tumour suppressor?

Points of contention

I can’t help but wonder why Jolie’s revelation is not being interpreted as further incentive for people to demand cheaper tests. If more people start wanting to take the BRCA test, won’t more people want to afford the test, thereby weakening Myriad’s case rather than strengthening it?

Was Angelina Jolie duped into spearheading a corporate PR stunt? Or is Angelina Jolie just an independent mother of six who is determined to live a long life as long as she has the means?

We’ll probably never know the full truth. What we can know is the truth of some facts.

Vague terminology and ambiguous sentences like “The mutant gene occurs very, very rarely" are being casually tossed around by the media. This is inadvertently introducing ill-formed opinions among the public.

The truth about the figures

Much of this ambiguity is a result of too many numbers and too many ways of interpreting them. The figures below are stated by the National Institutes of Health (NIH) and Stanford School of Medicine:

How common are BRCA mutations?

Around 1 in 500 individuals in the general population carries a BRCA mutation.

The probability increases when there is family history.

The probability also increases if you belong to a high-risk community such as the Ashkenazi Jews or some Brahmin sects in Western India. For example, 1 in 40 Ashkenazi individuals has a BRCA mutation.

Also worth noting is that most research has been done with large families with a history of cancer. So terms such as “general population” and risk estimates may change as more data becomes available.

How risky are BRCA mutations?

12 per cent of women in the general population will develop breast cancer sometime in their lives.

60 per cent of women who carry a BRCA mutation will develop breast cancer sometime in their lives.

That is a five-fold higher risk.

Are all breast cancers caused by BRCA mutations?

No. Among white women in the US, BRCA mutations account for 5-10 per cent of breast cancers.

This means, as Dr. Gilbert Welch stresses in a CNN.com article, about 90 per cent of breast cancer deaths have nothing to do with the BRCA mutation.

But it is also important to be reminded of the inverse of that statement. Sixty per cent of BRCA-mutation carriers will develop breast cancer. Angelina Jolie was one of these people. Her risk was estimated to be even higher, at 87 per cent, because of family history.

Now, debate if you must.

(Nandita Jayaraj writes about her encounters with the strange and interesting. You can send her feedback at nandita.j@thehindu.co.in. You can also tweet her @nandita_j)