[CRobin23 (OP)]

I read somewhere that mutations occur 1 every 1 billion base pairs. Since our cells are constantly dividing everyday, doesn't that mean that mutations in our DNA are steadily building up the longer we live. If this is true what's to stop a build up of mutations on an important enzyme or protein our body needs, therefore putting us in danger.

For example what if a mutation occurs in an important part of what codes for the enzyme lipase, and this cell divides and the mutation eventually ends up on many cells in the body. Pretty soon the body is barely able to break down fats, which could be problimatic. Or worse, a mutation occurs on an enzyme and causes it to break down something else that is important in our body.

I've never heard of scenarios like this happening, but if mutations can be random and can happen anywhere on the DNA what's to stop something like this from occurring.

[alancalverd]

1. Most of the DNA molecule seems to have no clear function. So most mutations will not affect any critical function.

2. Cells die all the time. A critical mutation will have no clinical effect if the mutated cell does not replicate before it dies.

3. Critical mutation is more likely to be fatal (to the cell) than malignant (allowing unlimited replication or viable dysfunction).

4. A potentially malignant cell is in a hostile environment: the immune system does not tolerate significantly "other" species, so even if a functionally mutant cell could survive in vitro, it will be challenged in vivo.

5. The overall statistics are such that most people survive around 60 - 70 years with no major malfunctions, after which various bits fail and we are nearly all dead by 100. Just as well, or there would be no room for our grandchildren.

6. The challenge to science, now that we have eliminated  famine, pestilence and most occupational hazards, is to rationalise the legal system so that we can choose when and how to die even if we are unable to deliver the fatal dose ourselves. Not a problem in principle, but other people's religion is the greatest cause of suffering among the terminally ill, and it is not amenable to logic.
 

[Hayseed]

See if you can find some Nova, or NG doc films on the wild mammals of Chernobyl.

It's quite an eye opener.

[evan_au]

if mutations can be random and can happen anywhere on the DNA what's to stop something like this from occurring.

Cells have a variety of DNA repair mechanisms, which manage to patch up most single-strand mutations.
And even many double-strand mutations.

Cells also have an audit mechanism, so that if a DNA repair fails, the cell commits suicide (apoptosis).

So the most important genes to protect are the genes governing this audit/apoptosis mechanism.
- Some of the first "cancer genes" discovered, relating to breast cancer do impact this audit mechanism
- Most malignant cancers have mutations in these pathways
- Elephants seem to have too few cancers for their size - but they also have multiple copies of these genes

See: https://en.wikipedia.org/wiki/DNA_repair
https://en.wikipedia.org/wiki/DNA_repair-deficiency_disorder