Prof Sir John Bell has been presenting a report on how the NHS should prepare for advances in the field.
He said missing out would come at a high cost to patients.
Health Secretary Andrew Lansley has announced plans to speed up the introduction of genetic cancer tests.
One of the problems with modern medicine is that some of the definitions of disease are too broad.
Prof Bell told the BBC: “Breast cancer has always been defined because it is a tumour in the breast.
“But if you look at the molecular detail of those cancers, some are much more similar to ovarian cancers than they are to other breast cancers, in molecular terms and in terms of their response to therapy.”
Cancer drugs are generally effective in fewer than one in three patients who take them, the report says.
The theory is that by looking at which genes are active inside a tumour, it will be possible to pick the correct treatment.
This is already happening in some cases. Bowel cancer patients with the defective gene K-RAS do not respond to some drugs, while the breast cancer drug herceptin works only if patients have a specific mutation, HER2.
One of the driving forces behind genetics in medicine is the plummeting cost of working out a patient’s genetic code. To sequence one patient’s genome once cost millions of pounds but it now costs thousands, and Prof Bell argues that in the future, the “cost could be essentially nothing”.
Prof Bell has previously accused the NHS of being “completely unprepared” for advances in the field of genetics. He has called for ministers to develop a strategy which would see the NHS adopting genetic tools, and training current and new staff in genetics.
He also wants a national centre which could store genetic information about patients who were sequenced. It would allow doctors to compare mutations in the genetic code with other patients who had the same mutation, to help plan treatment.
Prof Bell acknowledged that reforming the healthcare system to take greater account of genetics would require investment, but he added: “Innovation in any setting has to deliver a much better product or lower cost, or both, and I think genetics may be one of the things that does both.”
The government has yet to formally respond to the recommendations. However, Mr Lansley has announced plans to develop a new way of introducing and funding genetic tests for cancer.
“We want to make sure that all patients can benefit from these tests – as soon as the tests are recommended by NICE (the National Institute for Health and Clinical Excellence),” he said.
He compared the genetic code to a treasure map, saying the Xs were starting to appear, and that the promise of the field was “immense”.
The chief medical officer for England, Prof Dame Sally Davies, said genetics was “terrifically exciting” and would have an “increasingly important role” in areas such as cancer screening.
However, she said she was “quite worried” about some of the consequences, such the possibility that telling patients they had a low risk of developing lung cancer would give them a licence to smoke.