Presentation on theme: "8.1 Identifying DNA as the Genetic Material"— Presentation transcript:
18.1 Identifying DNA as the Genetic Material Set up Cornell Notes on pg. 3Topic: 8.1 Identifying DNA as the Genetic MaterialEssential Question:Summarize: Why was bacteriophage an excellent choice for research to determine whether genes are made of DNA or proteins?8.1 Identifying DNA as the Genetic Material2.1 Atoms, Ions, and MoleculesSummarize: Why was bacteriophage an excellent choice for research to determine whether genes are made of DNA or proteins?Key Concept:DNA was identified as the genetic material through a series of experiments
2KEY CONCEPT DNA was identified as the genetic material through a series of experiments.
3Frederick Griffith (1928)Microbiologist studying the bacterium that causes pneumonia to create a vaccineHe studied two typesS- smooth- Pneumonia + deathR- rough- Pneumonia + recovery
4Hypothesize what would Griffith expect to find if he combined the live S bacteria with live R bacteria?+
5Griffith’s Experiments Griffith injected the two types of bacteria into miceWhat should Griffith expect to find when he injects the S (encapsulated) bacteria into the mice?What about the R (non-encapsulated) bacteria?
6Hypothesize why only the S (encapsulated) strain would be deadly. The capsule protects the bacteria from the immune system!
7Hypothesize what happened when Griffith heat-killed the S bacteria and injected it into the mice. When Griffith heat-killed the S bacteria and injected it into the mice, they were unaffected (healthy and alive).
8Hypothesize what Griffith expect to find if he combined the dead S bacteria with live R bacteria?
9When Griffith injected mice with a combination of heat-killed S bacteria and R bacteria the mouse died!!!What do you think he found when he took a blood test of the dead mouse?
10When he did a blood test on the dead mouse he found live S bacteria in the dead mice!
11Table TalkHypothesize with your table about what happened when the heat-killed S bacteria was combined with the R bacteria.Remember:Live R= live mouseHeat-killed S= live mouseLive R + Heat-killed S= dead mouse
12A “transforming material” passed from dead S bacteria to live R bacteria, making them deadly.
13Oswald Avery, a biologist, spent 10 years trying to figure out what Griffith had discovered (1944) He combined R bacteria with an extract made from S bacteria and observed R bacteria turning into S bacteria.
14Wanted to know if it was DNA or protein that transformed harmless R bacteria into deadly S bacteria tests showed DNA was present when proteins were not.chemical makeup matched that of DNA.
15Avery’s Experiments (DEMO) Broke down the Heat-killed S bacteria into its componentsCarbohydratesLipidsProteinsDNARNAHe then added Live R bacteriaWhat should we expect to happen to each animal?Rabbit 1: CarbsT-Rex 2: LipidsRabbit 3: ProteinsSnail 4: DNAElephant 5: RNA
16Avery’s Experiments Cont’ (DEMO #2) Even though this was good evidence that DNA was the genetic material, more evidence was needed.This time scientists decided to add enzymes that destroyed specific components of the Heat-killed S bacteriaWhat should we expect to happen to each animal?Rabbit 1: Carb destroying enzymeT-Rex 2: Lipid destroying enzymeRabbit 3: Protein destroying enzymeSnail 4: DNA destroying enzymeElephant 5: RNA destroying enzyme
17Transformation ONLY stopped when an enzyme was added that destroyed DNA!!!
18He thought DNA was the transforming principle, but more proof was needed…
19Hershey and Chase studied viruses that infect bacteria, or bacteriophages. (1952)
20This confirmed that DNA was the genetic material! They tagged viral proteins with radioactive sulfurThey tagged viral DNA with radioactive phosphorusTagged DNA was found inside the bacteria; tagged proteins were not.This confirmed that DNA was the genetic material!