1. Biology 1-1b
DNA Replication

2. 1-1b: DNA Replication
Every cell in our body (except our reproductive cells) contains a complete copy of our DNA
This means that in order for cells to replicate (which they do all the time so we can grow, repair injuries, etc.) our DNA must replicate as well

3. 1-1b: DNA Replication
The structure of DNA makes replication quite simple
The two polynucleotide chains unzip from each other and then each chain is used as a template to build a new one!

4. Let’s take a closer look at the steps involved…

5. 1-1b: DNA Replication
A type of enzyme called a topoisomerase makes a nick in the double helix, beginning to allow a small portion of the DNA to unzip creating an area called a replication fork
Another enzyme, helicase, continues to unwind the DNA, lengthening the replication fork.

6. 1-1b: DNA Replication
Several small proteins called single strand binding proteins (SSB) temporarily bind to each side to keep them separated.
An enzyme called DNA polymerase “walks” down the DNA strands and adds new nucleotides to each strand. The new nucleotides bond to the complementary nucleotides on the existing strand (A with T, G with C)

7. 1-1b: DNA Replication
An enzyme called DNA ligase seals up the new fragments into one long continuous strand.
The new copies automatically wind up into a double helix again.

8. 1-1b: DNA Replication DNA polymerase connects nucleotide to nucleotide
DNA ligase seals the individual parts of the sugar-phosphate backbone together, creating a smooth new strand of DNA

9. 1-1b: DNA Replication
You may have noticed that one side of this replication fork looks much more complicated than the other…

11. 1-1b: DNA Replication
There is a lot more detail involved in DNA replication and you will learn more about it if you take Biology 11 and 12.
For Science 10, this is as complicated as we need to get 