Unit 3 Nucleic Acids. Nucleic Acid- A large complex organic molecule that stores and transmits...

Unit 3Unit 3Nucleic AcidsNucleic Acids

Nucleic Acid- Nucleic Acid-

A large complex A large complex organic molecule that organic molecule that stores and transmits stores and transmits genetic informationgenetic information

DNA & RNADNA & RNA

EvidenceEvidence

Supporting the role of Supporting the role of DNA in living things DNA in living things

Transformation-Transformation-

To change from one To change from one form to anotherform to another

Transformation ExperimentTransformation Experiment

S. Pneumoniae S. Pneumoniae BacteriaBacteria

R strain- harmlessR strain- harmless S strain- virulent S strain- virulent

(disease causing)(disease causing) Mice Mice

Experiment 1 with Bacteria (p194)Experiment 1 with Bacteria (p194)

R cells R cells injected injected mice live mice live

Experiment 2 with Bacteria (p194)Experiment 2 with Bacteria (p194)

S cells S cells injected injected mice die mice die

Experiment 3 with Bacteria (p194)Experiment 3 with Bacteria (p194)

Heat killed S cells Heat killed S cells injected injected mice live mice live

Experiment 4 with Bacteria (p194)Experiment 4 with Bacteria (p194)

R cells + heat killed S cells R cells + heat killed S cells injected injected

QuestionQuestion

1. Based on results of Exp 1, 2, & 3, what 1. Based on results of Exp 1, 2, & 3, what do you think happened in Exp 4?do you think happened in Exp 4?

Answer- Mice LiveAnswer- Mice Live 2. Could cells injected in Exp 4 cause 2. Could cells injected in Exp 4 cause

pneumonia before they were injected?pneumonia before they were injected? Answer- NoAnswer- No

Experiment 4 with Bacteria (p194)Experiment 4 with Bacteria (p194)

R cells + heat killed S R cells + heat killed S cells cells injected injected mice diemice die

QuestionsQuestions

3. How did the bacteria that resulted in Exp 4 3. How did the bacteria that resulted in Exp 4 differ from ones injected?differ from ones injected?

Answer- Living S cell present.Answer- Living S cell present. Read through the ExtensionRead through the Extension 4. Was this difference only in their structure?4. Was this difference only in their structure? Answer- No, since trait is passed on, the genetic Answer- No, since trait is passed on, the genetic

message must also have been changed.message must also have been changed.

QuestionsQuestions

5. Give an explanation as to what happened in 5. Give an explanation as to what happened in Exp 4.Exp 4.

Answer- Answer- DNA DNA from heat killed S cells used in R from heat killed S cells used in R cells & changes them into living virulent S cellscells & changes them into living virulent S cells

Transforming Factor-Transforming Factor-

Factor that causes Factor that causes the transformation- the transformation-

Avery tested in Avery tested in 1940’s, determined it 1940’s, determined it waswas DNA DNA

Bacteriophage (p. 195)Bacteriophage (p. 195)

A virus that infects a A virus that infects a bacteriabacteria

Consists of a protein Consists of a protein coat and DNAcoat and DNA

Problem- Is it the Problem- Is it the protein coat or DNA protein coat or DNA that is hereditary that is hereditary material a virus material a virus transfers to a transfers to a bacterium?bacterium?

Hershey-Chase Experiment Hershey-Chase Experiment (p 195 )(p 195 )

1. Used radioactive sulfur to tag protein 1. Used radioactive sulfur to tag protein coat.coat.

2. Used radioactive phosphorous to tag 2. Used radioactive phosphorous to tag the DNA.the DNA.

3. Used blender to separate the virus coat 3. Used blender to separate the virus coat from bacteria.from bacteria.

Detected radioactive phosphorous in the Detected radioactive phosphorous in the bacteria. Concluded DNA enters bacteria.bacteria. Concluded DNA enters bacteria.

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