DNA REPLICATION Overview Information Chromosome Structure DNA Replication

DNA REPLICATION Overview Information Chromosome Structure

DNA Replication The Beautiful Experiment A. Two Theories 1. Conservative replication a. one molecule made of “parent” DNA and the duplicate was all new DNA 2. Semi-conservative replication a. each new strand made of parent and new DNA or old and new hybrid B. Meselson and Stahl 1957 1. Determined that DNA replicated by means of semi-conservative mode

DNA Replication The Beautiful Experiment B. Meselson and Stahl 1957 1. Determined that DNA replicated by means of semi-conservative mode 2. Experimental design

DNA Replication The Beautiful Experiment B. Meselson and Stahl 1957

DNA REPLICATION Overview Information • Each strand of the DNA double helix has all the information needed to reconstruct the other half by the mechanism of base pairing. • In most prokaryotes, DNA replication begins at a single point and continues in two directions.

DNA REPLICATION Overview Information • In eucaryotes chromosomes, DNA replication occurs at hundreds of places. Replication proceeds in both directions until each chromosome is completely copied. • The sites where separation and replication occur are called the replication fork

DNA REPLICATION Overview Information • During DNA replication, the DNA molecule separates into two strands then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template for the new strand.

DNA REPLICATION

DNA REPLICATION BLANKSHEET

A T A C T G T C G A G G T A G C T C C A STARTING DNA STRAND A T T A C G A T C G G C A T G G G C T A DNA Helicase breaks hydrogen bonds

A T T A T C G A G G T G A G C T C C A DNA LADDER OPEN C G G A G G T T G A C T G C T A DNA Polymerase builds new strand a. Leading strand: built in continuous 5’ – 3’ direction b. Lagging Strand: built with Okazaki fragments in discontinuous 5’-3’ direction

A T A T C T G A C G A G G T G C T C C A Semi-conservative replication complete resulting in identical DNA copies consisting of old and new DNA C C A

DNA REPLICATION • Replication Enzymes 1. DNA Helicase: unwinds helix at replication fork 2. DNA polymerase: helps bonding of new nucleotides to template strand 3. DNA Ligase: bonds Okazaki fragments together