DNA Replication Lecture Notes PDF

Chapter 12: DNA Replication Accurate DNA replication in action! 1. The Central Dogma of Molecular Biology DNA Replication: Genetic Information Must Be Accurately Copied Every Time a Cell Divides Astoundingly accurate: even a low error rate of 1 in a million would result in 6,400 mistakes ever...

Chapter 12: DNA Replication Accurate DNA replication in action! 1. The Central Dogma of Molecular Biology DNA Replication: Genetic Information Must Be Accurately Copied Every Time a Cell Divides Astoundingly accurate: even a low error rate of 1 in a million would result in 6,400 mistakes every time a cell divides! Rapid: E. coli’s genome is about 4.6 million base pairs. If the replication rate was 1000 nucleotides per minute it would take over 3 days, yet E. coli are capable of dividing every 20 minutes! Actually, E. coli replicate at a rate of 1000 nucleotides per second with an error rate of less than 1 in a billion nucleotides!  Section Outline 1. DNA structure (review) 2. DNA Replication is Semi-Conservative 3. Modes of DNA replication 4. Features of DNA replication 5. Proteins involved in prokaryotic DNA replication 6. Unique aspects of eukaryotic DNA replication Pages to Omit from Chapter 12: Meselson and Stahl experiment in sections 12.2 and 12.4 and all of Section 12.5 on DNA recombination. 1. DNA structure Review of Chapter 10: BASIC FEATURES of DNA nucleotides and the DNA double helix Complementary base pairs (A pairs with T, G pairs with C) Three hydrogen bonds pair G with C, while two hydrogen bonds pair A with T Anti-parallel 5’ to 3’DNA strands Right-handed double helix (B- DNA): most common form in living cells Ten base pairs per turn 0.34 nm between stacked bases; 3.4 nm per helical turn 2. DNA replication is semi-conservative Back in the day, a central question was How does DNA replication occur? “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material” James Watson Francis Crick J.D. Watson and F.H.C. Crick. 1953. Nature 171: 737-738  2. DNA replication is semi-conservative The Watson-Crick double helical DNA model suggested a possible semi-conservative copying mechanism -after one round of DNA replication, each DNA contains 1 parental and 1 newly-synthesized strand 2. DNA replication is semi-conservative 2. DNA replication is semi-conservative Original DNA strands Conservative Dispersive Semi-conservative  3. Modes of DNA replication Prokaryote Chromosomes Eukaryotic Chromosomes  3. Modes of DNA replication 1. Theta replication -replication that occurs in most circular DNA (eg., bacteria with only 1 origin of replication that is 4.6 million nt in length) DNA replication is bidirectional * θ Greek letter theta  3. Modes of DNA replication 2. Rolling circle replication –specialized form of replication that occurs in the F factor of E. Coli and some viruses (only 1 origin of replication) DNA replication is unidirectional  3. Modes of DNA replication 3. Linear chromosome replication –occurs in the linear chromosomes of eukaryotic cells. DNA replication is bidirectional Mice have ~25,000 origins of replication and each replicon is about 150,000 nucleotides in length. 3. Modes of DNA replication