What prevents the wrong nucleotides from being added to the new strand during DNA replications?

Question

i know that the DNA polymerases add nucleotides to those according to the base-pairing rule (Chargaff's rule), but what prevents it from doing it wrong?
simple question, 10 points for the first person with the correct answer! =)

Answer 1

DNA pol. has a self correcting action that takes out a single incorrect base or a group of bases containing the error.

Answer 2

"Atheists, why is sexism and racism wrong but not anti-theism?" TWO are anti-person and the other is anti-concept. "A man doesn't choose religion. Religion chooses the man." Boolshiit... A man is usually PROGRAMMED with the religion of his parents, or country. "Nobody in his right mind wakes up one fateful morning and says... "I think I'll be an atheist today"." True but many wake up from the fantasy dream and realise it was a fantasy and thereby conclude that atheism is the logical position... Theism = belief in gods - a religious position - NOT a religion. Atheism = NO belief in gods - a religious position - NOT a religion. Atheism is a conclusion. An intellectually honest one. EVERYONE is born atheist = no belief in gods = not theist. Theism/atheism is about belief - not the how or why one arrived at that belief. “Humanity was plodding along and then one day some smartarze suggested thunder was caused by an invisible man in the sky. The atheist said “Büllshït!” We've been asking for evidence ever since. You never provided any... Cos if you did have some you wouldn't have to pull the "Have Faith" card. YOU are the people insisting an imaginary little hairy-nosed psychopath is swooping about in the ether doing the worst possible mayhem on innocent children... NOT I? If I told you I had a Pixie in my pocket I'm sure you'd ask to see it.. So what we are asking is... produce your Pixie ;)” Frank Zindler: Remember that the burden of proof is on the person alleging the existence of something. If someone tells me that the Easter Bunny is hiding in somebody's clothes closet somewhere in North America, there is no need for me to search every closet on the continent. The person making the claim has to produce the rabbit or stop wasting my time. [[edit]] @OP: "So far as I can tell, atheism is nothing more or less than a hate group." Naahhh... we just don't believe in invisible sky critters and you hate us for it. "The only way a person can demonstrate the absence of something (i.e. atheism) is by mocking and destroying the presence of something (i.e. religion)." As you people won't engage in Logic&Reason, Pointing&Larfing is all we have ;) ~

Answer 3

Enzymes put those nucleotides together like puzzle pieces. They only fit the right way.