快猫短视频

IN 2010, doctors may treat you for conditions such as cancer and heart
disease even before they appear. The sequencing of the human genome will lead to
a fundamental shift towards preventive medicine.

It鈥檚 all down to knowing what our genes are up to. 鈥淚f we identify the genes
involved, we can look at the pathways controlled by those genes, and try to
develop rational treatments based on this knowledge,鈥� says Nick Hastie, director
of the Medical Research Council鈥檚 Human Genetics Unit in Edinburgh. That means
drugs can be designed to correct the cause of a disease.

鈥淎t the moment, we know how a change in a gene product can lead to disease,鈥�
says clinical geneticist Sandy Raeburn of Nottingham University. 鈥淏ut in the
future, we are going to find out how different genes interact. It鈥檚 very
别虫肠颈迟颈苍驳.鈥�

Such discoveries will enable us to work out which combinations of genes and
environmental factors lead to disease. 鈥淭he most important role will be to
predict risk early, before problems develop,鈥� says Robert Plomin of the
Institute of Psychiatry in London.

A routine check-up in 2010 will perhaps involve giving a sample of blood or
cheek cells, from which your DNA will be extracted and screened to determine
your risk of developing various diseases. We already know the genes that cause
many rare, single-gene disorders, but in future you could be screened for common
diseases that appear in adulthood, such as type II diabetes, heart disease and
cancer, and perhaps even complex mental disorders such as schizophrenia and
depression.

Because these diseases have many contributory factors, both genetic and
environmental, the test results will give a percentage risk rather than a
definite yes or no. David Altshuler, a geneticist from the Whitehead Institute
for Biomedical Research in Cambridge, Massachusetts, believes the technique will
simply extend familiar tests. 鈥淧eople are comfortable with the idea of measuring
blood pressure or cholesterol and being told of any risk factors. It should be
the same with genetic screening. For patients it is not a death sentence, it is
information they can use.鈥�

But the screening will be more sophisticated than anything we know today. 鈥淲e
will not only be able to say who is at risk, we鈥檒l know whether their risk will
be reduced by various interventions,鈥� says Paul Kelly, head of the British
company Gemini Genomics of Cambridge. For example, while one patient might be
advised to eat a healthier diet to reduce their risk of heart disease, another鈥檚
genes might suggest that diet would make no difference and be prescribed
exercise or a cholesterol-lowering drug instead.

Screening will rely on superfast techniques of determining which gene
variants a person possesses, such as DNA chips. These are thin slices of glass
about the size of a postage stamp
(快猫短视频, 14 November 1998, p 46).
Stuck onto the surface in a grid are strings of DNA representing thousands
of gene variants. When a patient鈥檚 DNA is added to the chip, pieces stick to
matching strings, and the rest are washed away. Electronic scanners read the
matches, giving a 鈥測es/no鈥� for each gene within hours.

鈥淚 imagine a chip with around 100 relevant polymorphisms for a complex trait,
for example hypertension or schizophrenia,鈥� says Plomin. Each individual gene
may have a small effect, but by taking all the relevant genes together, an
overall risk for each disease can be calculated.

By 2010, doctors may also use gene screening to discover which drugs best
suit you. Our genes determine whether different drugs will work well or cause
side effects. For example, Alzheimer鈥檚 patients with a gene variant called
ApoE &egr;4 are much less likely to benefit from a drug called tacrine than
other patients.

Knowing which genes are active in particular cells is also important. Louis
Staudt of the National Cancer Institute near Washington DC hopes this will
enable us to classify tumours more precisely. 鈥淲e will end up rewriting the
textbook definition of most cancer types in the next few years,鈥� he says.

Staudt and his colleagues used a DNA chip to profile different samples of a
cancer called diffuse large B-cell lymphoma, and found there are actually two
distinct classes of disease, with different genes switched on in each. Cancer
cells from the two groups look identical under the microscope, but one set of
patients responded well to chemotherapy, while the other did not. Staudt hopes
that in the future this technique will routinely guide cancer treatment.