It DOESN'T???
Why not?
Perhaps an ID'er would suggest that a higher intelligence designed the chemical structure of RNA to do just what it does.
Perhaps a scientist will be able to show how something OTHER than a copy manages to get into the strand.
Since this is the very essence of Evolution, THAT is what is needed now to blast the IDer's out of the water.
As to your other point, the copying process is always prone to error (there's a whole lotta shaking going on down there). Most of the errors don't improve the fitness of the resulting organism, but some do. Hence the show goes on.
Since this is the very essence of Evolution, THAT is what is needed now to blast the IDer's out of the water.
By this standard, ID has already been blown out of the water. The error rates of DNA replication and polymerase transcription are well known, as are the types of errors and how they occur. Errors occur in the transcription of one out of every 10^4 to 10^5 base pair. DNA replication has an error rate that is approximately the same, but the DNA strand is checked twice for errors which increases accuracy. Note that I am talking about errors in the chemical assembly of proteins and the duplication of DNA. This does not include damage from environmental sources such as chemical carcinogens or radiation exposure, only errors in the transcription and duplication process.
Yes, that indeed is the question, and further, in a complex animal (bird, fish, reptile, or mammal) how would the changed molecule excape destruction by the immune system?