1 / 9

KEY CONCEPT DNA was identified as the genetic material through a series of experiments.

KEY CONCEPT DNA was identified as the genetic material through a series of experiments. Griffith finds a ‘transforming principle.’ . Frederick Griffith, a British microbiologists, experimented with the bacteria that cause pneumonia.

blenda
Download Presentation

KEY CONCEPT DNA was identified as the genetic material through a series of experiments.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. KEY CONCEPT DNA was identified as the genetic material through a series of experiments.

  2. Griffith finds a ‘transforming principle.’ • Frederick Griffith, a British microbiologists, experimented with the bacteria that cause pneumonia. • He used two forms: the S “smooth” form (deadly) and the R “rough” form (not deadly). • A transforming material passed from dead S bacteria to live R bacteria, making them deadly.

  3. Avery identified DNA as the transforming principle. • Avery isolated and purified Griffith’s transforming principle. • Avery performed three tests on the transforming principle. • 1. Qualitative tests showed DNA was present. • 2. Chemical tests showedthe chemical makeupmatched that of DNA. • 3. Enzyme tests showedonly DNA-degradingenzymes stoppedtransformation.

  4. Hershey and Chase confirm that DNA is the genetic material. • Alfred Hershey and Martha Chase, American biologists, studied viruses that infect bacteria, or bacteriophages. • They tagged viral DNA with radioactive phosphorus. • They tagged viral proteins with radioactive sulfur. • Tagged DNA was found inside the bacteria; tagged proteins were not. (This finding proved that genetic material is DNA not protein).

  5. Section 8.1 Assessment (BIO #1-3; BIO-CM #1-4) • (1) What was “transformed” in Griffith’s experiment? • (2) How did Avery and his group identify the transforming principle? • (3) Summarize how Hershey and Chase confirmed that DNA is the genetic material. • (4) CRITICAL THINKING. Why was the bacteriophage an excellent choice for research to determine whether genes are made of DNA or proteins?

  6. Answers to Sec 8.1 Assessment • (1) What was “transformed” in Griffith’s experiment? • Harmless R bacteria were transformed into pathogenic S bacteria.

  7. Answers to Sec 8.1 Assessment • (2) How did Avery and his group identify the transforming principle? • They purified the component of S bacteria that caused R bacteria to transform into S bacteria. This extract was tested for the presence of DNA or protein, its chemical composition, and its reaction to enzymes.

  8. Answers to Sec 8.1 Assessment • (3) Summarize how Hershey and Chase confirmed that DNA is the genetic material. • They labeled the protein of bacteriophages with radioactive sulfur and their DNA with radioactive phosphorous. The bacteriophages were allowed to infect bacteria. Hershey and Chase separated the phages from the infected bacteria and showed that phosphorous, a component of DNA, not sulfur, had entered the bacteria.

  9. Answers to Sec 8.1 Assessment • (4) CRITICAL THINKING. Why was the bacteriophage an excellent choice for research to determine whether genes are made of DNA or proteins? • A bacteriophage consists of little more than a protein coat surrounding DNA. The protein coat is left behind when the viral DNA enters a bacterium.

More Related