You will respond to medication differently to the person sitting next to you. A friend of a different race may be more susceptible to diabetes than you are; you could be at greater risk of developing hypertension.
These signposts – which point to your disease risks and whether a certain medication will work for you – can be read in your genes. But the populations of Southern Africa, where we have the greatest genetic diversity, are understudied. And if they are studied, this information often leaves the country.
"The race issue is contentious, but it's important," says Professor Michael Pepper, director of the Institute for Cellular and Molecular Medicine at the University of Pretoria.
"We don't want discrimination, but there are groups of people in which one can cluster different sorts of diseases."
For example, there is a high prevalence of diabetes among Indians, high cholesterol among Afrikaners and the black population is susceptible to certain heart conditions, namely cardiomyopathy, and also malignant hypertension, Pepper says. "If you are a clinician and someone walks into your office, you need to take everything into account in order to develop an idea of what their illness might be."
However, African genetic diversity has been neglected.
Understanding the interactions between genome structure and environmental influences is essential to interpreting their contributions to the increase in infectious diseases and noncommunicable diseases, exacerbated by adverse environments and lifestyle choices. This is according to Michele Ramsay, chair of the South African Society for Human Genetics and professor in the division of human genetics at the National Health Laboratory Service and Wits University.
She wrote an article in July last year for scientific journal Elsevier, titled "Africa: Continent of genome contrasts with implications for biomedical research and health".
"The unique genome dynamics in African populations have an important role to play in understanding human health and susceptibility to disease," she wrote.
Southern Africa is the site of colliding epidemics – infectious diseases, such as tuberculosis, HIV and malaria, and lifestyle diseases, such as diabetes, heart diseases and some cancers.
In another article, titled "Africa: the next frontier for human disease gene recovery" and published in journal Human Molecular Genetics in 2011, Ramsay and other South African researchers said: "Differences between populations are characterised by different [genetic] mutations and frequencies of disease-related variants."
These can determine a population group's susceptibility to infection as well as its severity, disease progression and how an individual will respond to vaccination and medicine, they write.
Despite being under-represented in genome sequencing, African populations have the greatest genetic diversity on the planet. This finding was published in 2010, following the full genome sequencing of a Bushman and of Archbishop Desmond Tutu by American Stephan Schuster and a team of international scientists.
A sore point among South African researchers is international research using African genetic material.
"We have not protected the interests of our own genetic diversity," says Pepper.
"People have flown in, taken the DNA of our people, analysed it elsewhere and built stellar careers on it, without feedback to people in the communities."
This is part of what the South African Human Genome Programme, funded by the department of science and technology and soon to be housed in the Medical Research Council, aims to do.
According to Ben Durham, director for biotechnology at the department of science and technology, "Africa is the origin of humanity and in Southern Africa we have the highest genetic diversity. We want to be able to safeguard for our benefit the genomic heritage that we have in Southern – not South – Africa."
The programme is looking at creating a database and creating skills for African scientists to take part in the global genetics push, he says.
The objective is to develop capacity for genomic research in Southern Africa and "translate that knowledge and information into advances in human health", says Ramsay.
Developing capacity is even more important. A comprehensive review of the country's genetics services and testing, published in 2008, found that the country had only 10 clinical geneticists for a population of 48-million people – even though the World Health Organisation recommends that geneticists form part of public healthcare.
But Ramsay says that capacity has declined even further in the past four years.
According to some health department officials, this is largely attributed to the policies of former health minister Manto Tshabalala-Msimang, who introduced a policy in 2001 that cut funding to provincial and academic hospitals for research.
But it is not just about genetics services. "Years of neglect will only show later through the collapse of the system," says department of health director general Malebona Precious Matsoso.
"Overhauling the health system is going to present an opportunity … Our investment should be in research and development technologies for diseases that disproportionately affect our country. In South Africa, we find the meeting of communicable and noncommunicable diseases," says Matsoso. "How do you treat someone who is HIV positive, but presents with diabetes, hypertension and has TB at the same time?"
Pepper says this is where genetics research can play a role.
"The kind of work we do would show why individuals respond differently to the drugs we given them. Think of the people in your social circle: they respond differently to different drugs. Some get ill, some don't respond at all, and some get better. Your genetics can predict that.
"This is especially important for HIV and TB. If the drug makes someone sick, then they won't take drugs. Lack of compliance [people not taking their medication] may lead to the emergence of resistance [because people do not take their medication regularly]," he says.
"If we can predict adverse drug reactions, we can alter doses or change medication."
However, although Africa needs to protect its genetic resources, "it must not be close-minded and overprotective … We must not miss the opportunity to collaborate with others," Pepper says.
There are a number of collaborations, such as the Human Heredity and Health in Africa (H3Africa) initiative, which focuses on the development of expertise on the continent and establishing networks of African investigators. H3Africa is funded by the Wellcome Trust, a United Kingdom-based charitable organisation that funds medical research.
However, although there are many benefits associated with genetics research, the challenges of stigmatisation and informed consent remain.
"In our [population groups], community and individual consent are key if this process is to work," Pepper says.
It is illegal to take people's genetic material without informed consent, and the South African Human Genome Programme prohibits the public disclosure and dissemination of genetic markers that could point to a population's susceptibility to disease, intelligence and sexual preference, among others, that could give rise to stigmatisation.