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Transcript
SBI4U – Molecular Genetics 493694377 Date: ___________________________ Hershey Chase Experiment Background Viruses are composed of ________ (or _________) inside a protein coat/shell called a ______________ It was also known that viruses replicate by taking over the host cell’s ____________________________ to make more virus Used a virus which infects a bacterium is called a ________________ because the host bacterium cell is __________ as the new virus particles leave the bacterial cell In order to do all this, the virus must inject whatever is the _________ ____________________ into the host cell Thus, people realized that the viral genetic code material had to be either its _______ or its __________________ The Experiment To answer this question, Hershey and Chase performed an experiment using a bacterium named __________________________, or ___________ for short and a virus called _____ that is a bacteriophage that infects E. coli When the new T2 viruses are ready to leave the host E. coli cell (and go infect others), they burst the E. coli cell open, killing it The results that Hershey and Chase obtained indicated that the viral ____________, not the _______________, is its genetic code material Hershey and Chase used ___________________ chemicals to distinguish between (___________) the _____________________ and the ____________ in T2 virus so they could tell which of those molecules entered the E. coli cells Page 1 of 3 SBI4U – Molecular Genetics 493694377 Some amino acids contain ______________ in their side chains If T2 is grown in E. coli with a source of __________________ ______________, the sulfur will be incorporated into the T2 protein coat making it radioactive DNA has lots of _____________________ in its phosphate (PO43-) groups If T2 is grown in E. coli with a source of ________________________________, the phosphorus will be incorporated into the viral DNA, making that radioactive Hershey and Chase grew two batches of T2 and E. coli One with radioactive __________________ One with radioactive ____________ These radioactive T2 were placed in ______________________________ of E. coli, but were left there only 10 minutes This was to give the T2 time to _______________ their genetic material into the bacteria, but not _______________ Next, still in separate batches, the mixtures were __________________ in a kitchen blender to knock loose any ________________________ not inside the E. coli but perhaps stuck on the _______________________ This would differentiate between the protein and DNA portions of the virus Page 2 of 3 SBI4U – Molecular Genetics 493694377 Each mixture was spun in a _______________ to separate the heavy ___________ (with any _________________ that had gone into them) from the liquid solution they were in (including any viral parts that had not entered the bacteria) The centrifuge causes the heavier ______________ to be pulled to the __________ of the tube where they form a pellet, while the light-weight viral “leftovers” stay suspended in the liquid portion called the ______________________ The pellet and supernatant from each tube were separated and tested for the presence of _____________________ Radioactive sulfur was found in the _____________________ Indicates that the protein did not go into the bacteria Radioactive phosphorus was found in the ______________________ Indicates that viral DNA did go into the bacteria Based on these results, Hershey and Chase concluded that __________ must be the genetic code material, not ________________ as many people believed Page 3 of 3