DNA Word of the Day Replicate: to copy

Review DNA has a _______ ________ shape. It is made up of 4 different _________. Each subunit has a _______, a ______ and a _______. The _______ and the _________ make up the backbone of the structure. These are held together with ________ bonds.

There are four bases _______,_______, ______ and ________. A always matches with _______ and C always matches with ________. The bases are held together by _______ _______ bonds.

What is next? We know that cells need to divide in a process called mitosis. We know that during this time DNA has to replicate. What is your question?

Explain this picture.

Here is what happens: An enzyme (helicase) unzips the DNA molecule at various places This unzipping breaks the weak hydrogen bonds We now have two separate strands of DNA

Next DNA polymerase bonds free floating nucleotides with the exposed bases. These form complimentary strands of DNA

Next Each new strand of DNA has one new side and one side from the original DNA. This is called semiconservative replication.

DNA Facts In human cells 50 new nucleotides are added every second. It takes days to replicate one strand of DNA DNA polymerase can correct errors Error rate is 1 in a billion What do you think happens if we have too many errors?