DNA Replication 1DNA is capable of replicating itself

DNA Replication

� 1)DNA is capable of replicating itself. Every time a cell divides, each DNA strand makes an exact copy of itself. � 2)DNA directs the production of proteins in the cell. DNA contains the instructions on how to make proteins. DNA Does 2 Important Things in a Cell:

During the S phase of Interphase, the DNA strands (chromosomes) are replicated. The Cell Cycle

DNA replication occurs once in the life of a cell—right before it divides into two daughter cells. DNA strands replicate so that each new daughter cell has its’ own copy of the DNA instructions. Why does DNA replicate?

The deoxyribose sugar has 5 carbons. Carbon 1 is attached to the nitrogen base. Carbons 3 and 5 are attached to Phosphate groups. These are called 5’ and 3’ ends. DNA strands are anti-parallel

1) Helicase unwinds the DNA molecule and opens up the hydrogen bonds between the base pairs. The place where the DNA is opening up is called the Replication Fork. Single-stranded binding proteins (SSBs) hold the DNA strands open. DNA Replication, Step 1

DNA Polymerase adds nucleotides to the strands, one base at a time. The bases are added to their complimentary bases, according to the base-pairing rules: A bonds to T C bonds to G This will make 2 strands of identical DNA Replication, Step 2

�DNA polymerase cannot add nucleotides to an existing “open” strand by itself. �First, a short piece of RNA (called a primer) must be added to the open strand by Primase. Later on, the RNA primer will be removed and replaced with DNA Replication—a few more details

DNA Polymerase can only add nucleotides in the 5’ to 3’ direction. Therefore, one of the new strands will be made continuously. This is called the leading strand. The other strand must be made in pieces called Okazaki fragments. This strand is called the lagging strand. DNA Replication—More details

�http: //www. youtube. com/watch? v=te. V 62 zrm 2 P 0 DNA Replication Diagram

http: //www. youtub e. com/watch? v=zd Dki. Rw 1 Pd. U&feature =related http: //www. wiley. c om/college/pratt/04 71393878/student/ animations/dna_rep lication/index. html DNA Replication Animations

�What is the purpose of each of these enzymes? �A. Helicase �B. DNA Polymerase �C. Single Stranded Binding proteins (SSBs) �D. Primase �Why does DNA replicate with a leading strand a lagging strand—why don’t both strands replicate the same way? Quick Quiz

Name each part of this diagram: