Chapter 14 DNA Replication and Repair How are genes copied and passed onto offspring What are genes made of Protein or DNA Proteins Thousands of complex reactions are perforemed by them Proteins are complex 22 Amino acids to choose from Limitless variation in structure and fn DNA Though to be simple repetitive structure Known to be composed of just 4 types of deoxyribonucleic acids Hershey Chase Experiment 1 Hershey and Chase knew that T2 infections begin when the virus attaches to the cell wall and injects its genes into the cell s interior 2 Also knew the T2 is made up almost exclusively of proteins and DNA But was it protein or DNA that enters the host cell and directs the production of new viruses Hershey Chase Experiment What are some fundamental differences between the chemical make up of protein and DNA 1 DNA contains Phosphorus but not sulfur 2 Proteins contain Sulphur but not phosphorus Used a radioactive isotope of Sulphur 35S or a radio active isotope of Phosphorus 32P to produce a population of viruses with radioactive proteins and a population with radioactive DNA What would you expect if genes consisted of DNA Then the radioactive DNA should be inside the cells and radioactive protein should only be found in the capsids outside What would you expect if genes consisted of protein Only radioactive protein and no DNA should be found inside the cell The Primary Structure of DNA DNA has polarity meaning it has One end has an exposed phosphate on the 5 end and the 3 end has an exposed hydroxyl group The Secondary Structure of DNA How is DNA Replicated 3 Possibilities Conclusion DNA replication is Each newly made DNA molecule comprises one old strand and one new strand How is this accomplished Getting Replication Started Initially the replication bubble forms at specific sequences of bases called the and is bidirectional Getting Replication Started How is the helix opened and stabilized Getting Replication Moving How is the leading strand synthesized Getting Replication Moving How is the leading strand synthesized Getting Replication Moving How is the leading strand synthesized Getting Replication Moving How is the lagging strand synthesized Summary of DNA Synthesis What Happens When We Get to the End How do Eukaryotes keep their linear chromosomes Correcting Mistakes in DNA Synthesis DNA Polymerase can proofread Correcting Mistakes in DNA Synthesis DNA Polymerase can proofread DNA Repair and UV Damage Get in your groups
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