DNA REPLICATION An Overview of the Process

Defined…  DNA Replication  Prior to dividing, a cell will replicate its DNA to ensure that each new cell has a complete set of DNA molecules

Defined…  DNA Replication  This is when the double helix is separated into 2 separate “template” strands by an enzyme called helicase, so that an enzyme called DNA polymerase can pair free floating bases to the “template” strand forming a new “complimentary” strand, thus duplicating the existing supply of DNA molecules …whoa

As usual…  Let’s take this one step at a time:  When and where does this happen?  How are the 2 sides of DNA separated?  How is the new DNA made?

The Background Info:  Remember:  DNA is the molecule that is made of phosphate groups, deoxyribose sugar groups, and nitrogenous bases organized in a long, double helix shape, and stores our genetic information  In other words, our genes are in our DNA

The Background Info:  Remember:  The cell cycle consists of a series of steps: Interphase G1: cell growth S: Chromosome replication/DNA synthesis G2: organelles essential to division are made M Phase Mitosis Prophase Metaphase Anaphase Telophase Cell Division Cytokinesis

When and Where?  Now that we remember that, let’s put it together with what we’re learning about DNA replication…  DNA is separated into 2 halves (called 2 separate “strands”) and replicated during the synthesis stage of the cell cycle (called S phase)  This occurs while DNA is in the cell’s nucleus

How is DNA Separated?  The 2 sides of the DNA molecule are separated into 2 separate “strands” by an enzyme called helicase

Key Info:  An enzyme called helicase?  Back up: an enzyme is a protein that acts as a biological catalyst  Back up further: a catalyst is a substance that speeds up the rate of a chemical reaction  Put it together: helicase is a substance made of protein that acts during the process of DNA replication

How is DNA Separated?  As you can see, helicase “unzips” or “unwinds” the double helix of DNA into 2 separate strands by breaking hydrogen bonds between bases  You are left with 2 template strands  A template strand is a strand of DNA that you can use to build another matching strand, thus making more DNA replication bubble

How is New DNA Made?  With the 2 template strands separated, we can see how new DNA is made:  Another enzyme called DNA Polymerase attaches free floating bases to the template strands following the rules of base pairing  (A with T, G with C)  Take a look…

How is New DNA Made?

 Better yet, watch this youtube clip!

Better Yet…