IB SL BIOLOGY TOPIC 7 NUCLEIC ACIDS HL INTERNATIONAL BACCALAUREATE COMPLETE STUDY GUIDE 2023.

Hershey & Chase experiment Experiment target: T2 Bacteriophage (a kind of virus, containing DNA and a protein coat) & E.Coli bacteria How does virus work? • Virus injects their genetic material into cell • Non-genetic part of the virus (protein coat) remains outside the cell • Infected cell produces large amount of viruses based on the genetic material in the cell • The cell bursts releasing copied viruses Experimental methodology: • Amino acid containing radioactive isotopes were used to label the virus: 35S is used for labelling the protein coat, and32P is used for labelling DNA • Centrifuge is used for vigorous shaking in order to separate virus and infected bacteria: Pellet (solid) contains bacteria and supernatant (liquid) contains protein coat. Findings: • When protein coat is only radioactively labelled, new viruses made shown no radioactive sign • When DNA is only radioactively labelled, new viruses made shown radioactive sign Hypothesis: DNA controls genetic information. Rosalind Franklin’s and Maurice Wilkins’ investigation of DNAs tructure by X-ray diffraction Rosalind Franklin is the first women to take a photo of DNA using x-ray diffraction. Her investigation leads to the findings that DNA is a double helix.