DNA Replication: Chapter 10.4-10.5 PDF

“If you find a path with no obstacles, it probably doesn’t lead anywhere.” Anonymous  Chapter 10 Section 4-5: DNA Replication Learning Objectives ▪ Today you will learn to: ▪ Describe the basic structure of DNA and its function in inheritance. ▪ Explain the...

“If you find a path with no obstacles, it probably doesn’t lead anywhere.” Anonymous  Chapter 10 Section 4-5: DNA Replication Learning Objectives ▪ Today you will learn to: ▪ Describe the basic structure of DNA and its function in inheritance. ▪ Explain the process of DNA replication. Unit Organizer DNA & Viruses is about The Code of Life the Historical its Experiments how it is to discover it Structure Replicated for cell division Shape Components  DNA and Chromosomes ▪ Most prokaryotes keep a single DNA molecule located in the cytoplasm containing nearly all of the cell’s genetic information  DNA and Chromosomes ▪ Many eukaryotes have 1000 times the amount of DNA as prokaryotes. ▪ Eukaryotic DNA is located in the cell nucleus inside chromosomes during division and loose as chromatin during interphase. ▪ The number of chromosomes varies widely from one species to the next.  Eukaryotic Chromosome Structure Chromosome Nucleosome DNA double helix Coils Supercoils Histones  Fun Fact ▪ The DNA of the 46 chromosomes in one of your cells laid end to end would stretch to a length of more than 2 m, but it must coil up to fit into a nucleus only 5 µm in diameter!  Chromosome Structure ▪ Eukaryotic chromosomes contain DNA and protein, tightly packed together to form chromatin. ▪ Chromatin = DNA tightly coiled around proteins called histones. ▪ DNA and histone molecules form nucleosomes. ▪ Why would a cell need to have its DNA molecules tightly condensed into chromosomes during cell division ▪ To prevent tangling and to make separation and division of the chromatin more efficient during mitosis  DNA Replication ▪ Before dividing, a cell duplicates its DNA in a process called replication ▪ Replication ensures that each resulting cell will have a complete set of DNA  DNA Replication ▪ In eukaryotes, DNA replication occurs at hundreds of places. ▪ Replication proceeds in both directions.  DNA replication depends on specific base pairing ▪ DNA replication follows a semiconservative model. ▪ The two DNA strands separate. ▪ Each strand then becomes a template for the assembly of a complementary strand from a supply of free nucleotides. Animation: DNA Replication Overview Click on animation to activate Figure 10.4a-1 A T C G G C A T T A A parental molecule of DNA Figure 10.4a-2 A T A T A T C G C G G C G C G C A T A T T A T Free nucleotides A A parental The parental strands separate molecule of DNA and serve as templates Figure 10.4a-3 A T A T A T A T A T C G C G G C G C G C G C G C G C G C A T A T A T A T T A T Free nucleotides A T A T A A parental The parental strands separate Two identical daughter molecule of DNA and serve as templates molecules of DNA are formed Each newly replicated “daughter” DNA molecule consists of one parental strand and one new strand. Animation: Origins of Replication Click on animation to activate  The Role of Enzymes ▪ DNA replication is carried out by enzymes that “unzip” the molecule of DNA. ▪ Hydrogen bonds between base pairs are broken and the two strands of DNA unwind. New Strand Original strand Nitrogen Bases Growth Growth Replication Replication Fork Fork DNA Polymerase  The Role of Enzymes ▪ The main enzyme involved in DNA replication is DNA polymerase. ▪ DNA polymerase joins individual nucleotides to produce a DNA molecule ▪ It also “proofreads” each new DNA strand to prevent mistakes. Section Review 1. Describe the basic structure of DNA and its function in inheritance. Shape and organization 2. Explain the process of DNA replication.