1. KEY CONCEPT DNA replication copies the genetic information of a cell.
Main Idea 1. 2. 3.
Vocabulary Replication The process by which DNA is copied during the cell cycle. DNA Polymerase An enzyme that forms bonds between nucleotides during replication. Semi-Conservative Each DNA molecule contains an original strand of DNA and one new strand of DNA.

2. Replication copies the genetic information.
A single strand of DNA serves as a template or a pattern for a new strand.
The rules of base pairing direct replication. A=T C=G
DNA is replicated during the S (synthesis) stage of the cell cycle.
Each body cell gets a complete set of identical DNA.
EX: Your brain cells know how to make skin cells, but they don’t use this information.

3. Proteins carry out the process of replication.
DNA serves only as a template (pattern).
Enzymes and other proteins do the actual work of replication.
Enzymes unzip the double helix
In both directions.
Free-floating nucleotides form hydrogen bonds with the template strand.
nucleotide
The DNA molecule unzips in both directions.

4. DNA polymerase enzymes bond the nucleotides together to form the double helix.
Polymerase enzymes form covalent bonds between nucleotides in the new strand.
DNA polymerase
new strand
nucleotide

5. DNA replication is semiconservative.
Two new molecules of DNA are formed, each with an original strand and a newly formed strand.
DNA replication is semiconservative.
original strand
new strand
Two molecules of DNA

6. Replication is fast and accurate.
DNA replication starts at many points in eukaryotic chromosomes (it is faster and more efficient this way).
There are many origins of replication in eukaryotic chromosomes.
DNA polymerases can find and correct errors.
If a part of the DNA is incorrect only that part is repaired.