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Objective: Discuss DNA and base pairing

This discussion covers key experiments in the discovery of DNA and its role in genetics. We begin with Griffith’s experiment, which revealed bacterial transformation, and follow with Avery’s findings on the importance of DNA in genetic transmission. The Hershey-Chase experiment further solidified DNA's role over proteins. The structure of DNA is defined through nucleotides and base pairing rules established by Chargaff. We also discuss Rosalind Franklin's contributions through X-ray diffraction and the subsequent double helix model proposed by Watson and Crick.

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Objective: Discuss DNA and base pairing

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  1. Objective: Discuss DNA and base pairing 12.1

  2. Griffith’s experiment: Injected disease causing bacteria into mice They died Injected harmless bac. Into mice They lived Injected heat-killed disease causing bac. Into mice They lived Injected harmless bac. And heat-killed disease causing bac. Into mice They died

  3. Transformation- when one strain of bacteria is changed into another strain What caused it to change? DNA

  4. Avery: Tried to see if bacteria would still undergo transformation if only DNA was present Determined: DNA stores and transmits genetic info.

  5. Hershey-Chase experiment: Further showed DNA is what stores/transmits genetic info (not protein) Used radioactive markers for the protein in one experiment and radioactive markers for the DNA in the other experiment.

  6. What is DNA made of? Nucleotide- 5-carbon sugar, phosphate group and nitrogenous base Nitrogenous base Adenine, Guanine Cytosine, ThyminePurinesPyrimidines

  7. Chargaff’s rule: same number of Adenines (A) as Thymines (T) same number of Guanine (G) and Cytosine (C) Base pairing: A pairs with T G pairs with C

  8. Rosalind Franklin- used X-rays to determine shape of DNA. DNA had a cross shaped pattern Watson and Crick- used Franklin’s photos to come up with shape of DNA- double helix Double helix- twister ladder

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