Cells Are Often Ground Up with Abrasive to Get to Their

question 9

Multiple Choice

Cells are often ground up with abrasive to get to their internal enzymes/molecules, followed by removal of the abrasives. Here are three situations and three outcomes. What is the correct interpretation of the results?
In situation #1, radioactive amino acids are added to cell material, and radioactive proteins are produced.
In situation #2, radioactive amino acids, cell material, and the enzyme DNAse (degrades DNA) are added together. Radioactive proteins are still produced.
In situation #3, the ground-up cell material is allowed to sit for 24 hours before radioactive amino acids and DNAse are added to it. No radioactive protein is produced. What is the most likely interpretation?

• A) RNA polymerase has no activity after 24 hours, so no mRNA is transcribed and translated into radioactive proteins in the last scenario.
• B) The radioactivity in the amino acids is altering/degrading the tRNA molecules, leading to no protein production in the last scenario.
• C) Natural RNAses present in the ground-up material will degrade any existing mRNAs in that 24-hour interval. Added DNAses break down DNA so that new RNAs are not synthesized. This will lead to a loss of capability to translate protein in the last scenario.
• D) The radioactivity in the amino acids completely disappears within 24 hours. Transcription and translation occur as usual, but there is no radioactivity left in the system, so proteins are untagged.
• E) No conclusions can be made from the information given. More results are needed to interpret these experiments.