Why can't doctors/medical researchers fix abnormal or broken genes?

Answer 1

If only it were so easy. Gene therapy is an emerging field, and there is still a huge amount that we don't know, but basically, because it's a very hard problem and we're just not there yet.
In order to "fix" a gene, first you would have to know exactly what was wrong and where, so you need an easy and affordable way to sequence huge chunks of genome, which we don't have, the human genome project took dozens of labs years and years and that was just to sequence the genome of one person.
Secondly, when we found the gene we were looking for, now we have to have an easy way to synthesize a replacement, which we could probably do, but do not do regularly because now there's no point.
Finally, you have to find a vector that will put the new gene where it is needed and only where it is needed. We've been experimenting with various ways to do this, and so far we're not even close to having a good one.
So basically, because it's a really, really hard problem, but we're working on it ^_^.

Answer 2

They can 'fix' some abnormal genes, by a variety of testing (sometimes pre-natal) and therapies, or they can recommend a diet regime that would prevent the malign effects of the gene from manifesting themselves.

There are two problems. First, not all genes are equally amenable to the necessary treatment, which means isolating them (if a condition is genetic but involves the interaction of a number of genes it gets more complicated).

The second problem is political. President Bush signed into law various prohibitions that stopped researchers from doing the work that they needed to on blastocysts (i.e. very early embryonic tissue which only the most self-assured ignorant superstitious person could classify as a human soul ... a great many blastocysts are 'discarded' with a menstrual period and the woman's completely unaware that she had a conception) and so there's a whole range of genetic diseases within reach of scientists that can't be researched in the USA, despite pleas from many serious people - Christopher Reeve, to quote just one.

Answer 3

They're working on figuring it out right now!