Learning objective  SWBAT: Create a model that represents how genetic information is copied for transmission between generations and how that information is translated into poly peptides

Central Dogma = the flow of genetic material from DNA to protein

DNA Replication  DNA replication is semiconservative.  This means that, after replication, each daughter cell has one old DNA strand and one that is newly synthesized.

 If each of the 2 antiparallel strands can act as a template, they must first be separated from one another.  Replication begins at sites along the DNA called origins of replication.

 The process of replication requires numerous enzymes and proteins.  The double helix is untwisted and the two strands separated by helicase.  This creates a replication bubble.

 Bacteria have circular DNA and a single replication bubble.  Eukaryotic linear chromosomes may have 100’s or even 1000’s of these bubbles.

 At each end of the bubble is a Y-shaped region where the parent strands are being unwound by helicase called a replication fork.  Single strand binding proteins then attach to the strands to prevent them from re-linking.

 As the helix unwinds, tension is created as the strands on either end of the replication forks are wound tighter.  Topoisomerase relieves the tension by breaking, swiveling, and re joining the DNA.  Topo = place  Isomer = same composition, different structure or arrangement  Ase = ENZYME

Figure Single-strand binding proteins Helicase Topoisomerase Primase Replication fork RNA primer

 DNA polymerases then catalyze the elongation of the the new DNA at the replication forks by adding nucleotides matching A to T and G to C, but They can only add nucleotides; they cannot start the process. 2. They can only add to the 3´end of a growing chain, i.e. they work in a 5´to 3´direction.

 The initial nucleotide chain is actually RNA and is synthesized by RNA primase.

Figure Single-strand binding proteins Helicase Topoisomerase Primase Replication fork RNA primer

 Let’s see what this looks like with a model.  Please take:  2 green strands  2 white strands  1 burgundy strand  Dry erase board  Dry erase markers  Tape – to be shared  Scissors- to be shared

Proofreading and Repair  DNA ligase connects Okazaki fragments  Other enzymes correct incorrectly matched nucleotides.

 While not part of this PowerPoint, you must understand:  Leading vs. lagging strands  Okazaki fragments

Learning objective  SWBAT: Create a model that represents how genetic information is copied for transmission between generations and how that information is translated into poly peptides