Why is the rate at which mutations occur rather slow?

Answer 1

The simple answer is that the enzyme that replicates our DNA during cell division (DNA polymerase) not only has the ability to copy the DNA template, but also contains "proof-reading" activity (ie: if an error is made during DNA synthesis, the polymerase can back up, remove the error, and insert the correct base in the sequence). This proof-reading activity makes the naturally occuring mutation rate extremely low.

Answer 2

Because mutations are rare events. Mutations are the result when DNA is changed by interaction with cosmic rays. The only way a mutation can be passed on is by reproduction, and the mutation has to occur in the cells specifically used in reproduction, which makes then even more rare. So, if a mutation happens in me today, I have to have a child to pass that one on into the next generation, and then my child has to grow and have children. We are talking rare events and a full generation before the next generation can pass it on, and each generation has to have multiple offspring for the occurances of the mutation to appear in a larger portion of the population in general. And then it depends on what the mutation does. It can be good, enhance survivability, which means a better chance of procreating. It can be benign, neither helping or hurting survivability. Or, it can be detrimental, which means less survivability and a better chance of NOT being passed on to the next generation. I think you can see, that it will take many generations of multiple offspring before a given mutation will become significant, which is why we don't change all that much from year to year, but we have changed quite a but from what we were thousands of years ago. The same applies to every living thing. Change happens randomly, and very, very slowly. The one factor which speeds up the process is a shorter reproductive time, so more generations happen per unit time, but then, there is less chance of a singular random event causing a given mutation. More chances to be passed on, but less of a chance it happens in the first place.

Answer 3

Mutations are a random change in the DNA code. If this change happens in a place that causes an essential protein to not perform how it should, this could be a fatal problem and the organism might not even be born/conceived. In addition, the genome for any higher organism (eg. multicellular) is nearly inconceivably huge, being on the order of Billions of base pairs in length. Since before the Human Genome Project began, it's been observed many times that the # of genes is very small compared to the space they have available in the genome. This means that there's lots of dead space. Kinda like having a million square foot Walmart with only 5 items displayed right next to the one cash register (This isn't to say the extra space isn't useful though for both the Walmart and your genome!!). So combine the sparcity of the actual genes in the genome with the fact that many mutations are lethal, it adds up to a few mutations that are "tolerated" and a very very few select mutations that are "beneficial."

I hope this helps. :)

Answer 4

It's quite variable, but the essence is that DNA fidelity is important for health of the cell and by extension the organism. In mamallian cells, the DNA mutation rate is around 1 per 10^9 basepair (bp). So you could imagine that only a few mutations will occur each generation, ie from your parents to you. But in retroviruses, reverse transcriptase is around 1 per 1000 (10^3), here replication infidelity actually contributes to virus survival since it means its constantly changing. In fact for HIV the virions in a infected individual are somewhat genetically different, which is a phenominal mutation rate. Also note that on a evolutionary scale, generation time is very short for bacteria, while in mammals its very slow. So bacteria evolve much much faster than us (also their replication fidelity is about10,000 fold less than mammals).