(02/11/11) Lecture by Kevin Ahern of Oregon State University discussing Biochemistry Basics in BB 451. See the full course at oregonstate.edu This course can be taken for credit (wherever you live) via OSU’s ecampus. For details, see ecampus.oregonstate.edu Download Metabolic Melodies at www.davincipress.com Related courses include BB 350 – oregonstate.edu BB 450 – oregonstate.edu BB 100 – oregonstate.edu Highlights DNA Replication II 1. 1.DNA polymerase I has three enzymatic activities – a 5′ to 3′ DNA polymerase activity, a 3′ to 5′ exonuclease activity (also called proofreading), and a 5′ to 3′ exonuclease activity. 2. All DNA polymerases require a primer to start DNA synthesis. The primer is formed inside of cells by a special RNA polymerase known as primase. (RNA polymerase does not require a primer) 3. DNA replication proceeds by two distinct mechanisms (both 5′-3′, however)- one on each strand. Leading strand and lagging strand synthesis occur by different mechanisms, but both are catalyzed by the same DNA replication complex (Pol III, in the case of E. coli). 4. Leading strand synthesis is continuous in the 5′ to 3′ direction. Lagging strand synthesis can only occur when the leading strand synthesis opens up a new single stranded region for replication. The 5′ to 3′ syntheses of the lagging strand are discontinuous. The many pieces of lagging strand synthesis are called Okazaki fragments. 5. Okazaki fragments must be combined together ultimately. First, the RNA …