2. 1. What experiment proved the semi- conservative replication nature of DNA? 2. What are the 3 steps of the DNA replication process? 3. What proteins help to prevent the re- joining of base pairs? 4. What is the replication bubble?

3.  RNA primase brings the replication process by building a small complementary RNA segment on the strand at the beginning of the replication fork  These short ribonucleotide pieces of RNA are called RNA primers

4.  Nucleoside triphosphate  a building block and energy source for replicating DNA  DNA polymerase builds the new strand of DNA using nucleoside triphosphates

5.  As the replication fork continues to open and separate the parent strands, one strand is oriented in the 3’ to 5’ direction while the other is oriented in the opposite direction  recall, nucleotides can only be added to the 3’ end of the DNA strand

6.  RNA primase  makes RNA primers  DNA polymerase III  adds DNA nucleotides to the RNA primer  Since DNA polymerase III only builds the new strand in the 5’ to 3’ direction  DNA polymerase III that is building a strand toward the fork is able to keep moving forward continuously  leading strand

7.  Opposite strand  DNA polymerase III moving away from replication fork  lagging strand  RNA primase attaches another primer to the parent strand  another DNA polymerase III begins  these short DNA fragments are called okazaki fragments

8.  Completion of lagging strand: DNA polymerase I removes the RNA nucleotides and replaces with DNA nucleotides  DNA Ligase : catalyzes the formation of a phosphodiester bond between 2 DNA strands as well as between the Okazaki fragments

9.  DNA polymerase  also proofread and correct errors  Usually base pair mis-matches  DNA repair complexes read strands for errors missed by DNA polymerase III