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DNA: the hereditary material

DNA: the hereditary material. Unit 2: Molecular Genetics. What is the hereditary material?. You are a scientist. I t’s 1904. No one knows what type of material in a organism is the hereditary material. The “Old Model” of DNA through scientists off. #1: MIESCHER.

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DNA: the hereditary material

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  1. DNA: the hereditary material Unit 2: Molecular Genetics

  2. What is the hereditary material? You are a scientist. It’s 1904. No one knows what type of material in a organism is the hereditary material. The “Old Model” of DNA through scientists off.

  3. #1: MIESCHER • 1869 – Friedrich Miescher investigated chemical composition of DNA using pus cells. • At the time, proteins were thought to be hereditary material. • Miescher discovered the nuclei of cells contained a substance that does not act like protein. He called this substance nuclein.

  4. Hereditary Material? Protein? Nuclein (DNA)?

  5. VIDEO

  6. #2: HAMMERLING Location of Hereditary Information • 1930s • Acetabularia • one celled green alga.

  7. HAMMERLING: Location of Hereditary Information Cap Removed New Cap Regeneration

  8. HAMMERLING: Location of Hereditary Material Foot Removed No Foot Regeneration

  9. Hereditary Material? The nucleus contains the hereditary information... Nucleus contains chromosomes known to be responsible for inheritance, yet chromosomes consists of both DNA and proteins. Protein? DNA?

  10. GRIFFITH • 1920s - Frederick Griffith was trying to develop a vaccine against pneumonia. • He obtained unexpected experimental observations that led him to believe that protein is not the hereditary material.

  11. #3: GRIFFITH Streptococcus Pneumoniae

  12. Hereditary Material? Some substance (“the Transforming Principle”) must have been transferred from the dead bacteria to the living non-virulent bacteria making it virulent!

  13. VIDEO

  14. Avery, McCarty, MacLeod… • 1944 – Avery, McCarty, MacLeod later showed that the Transforming Principle was DNA!

  15. ERWIN CHARGAFF • 1949 – Chemical Difference between DNAs of different species were noticed by Chargaff. • He noticed: • The four different nucleotides were not present in equal amounts. • In some organism A & T predominate, in others G & C do. • A & T generally the same • G & C generally the same • A+T/G+C ratio is the same for all tissues of a species, but varies species to species.

  16. What does that mean… So maybe the structure of DNA proposed in 1904 isn’t correct…

  17. Alfred D. Hersey & Martha Chase • 1952 – Hershey & Chase conducted experiments using a virus that infects a bacterial host (bacteriophage) T2.

  18. Alfred D. Hersey & Martha Chase

  19. VIDEO

  20. DNA is the hereditary material! Amazing!

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