quiz2_s - MIT Department of Biology 7.014 Introductory...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
MIT Department of Biology 7.014 Introductory Biology, Spring 2005 Solutions to 7.014 Quiz I I Class Average = 79 Median = 82 Grade Range % A 90 - 100 27 B 75 - 89 37 C 59 – 74 25 D 41 – 58 7 F 0 – 40 2
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
TA:____________________ Question 1 (29 points) Barney is an alien. On his ship, hidden in the Stata building, you find alien bacteria that metabolize wood. You call this species A. termiticus , and call your original strain BLT (for “Barney’s little termiticus”). You subject a sample of BLT to mutagens, and isolate a new strain that no longer metabolizes wood. You conclude that you have succeeded in disrupting at least one gene necessary to metabolize wood. You call the mutant strain M. You mix a sample of M with a sample of heat-killed wild type BLT, and the resulting strain metabolizes wood. You summarize your data in the following table: Strains Metabolizes wood? BLT Yes Heat-killed BLT No M No Heat-killed BLT +M Yes a) Did the content of any of the BLT or M cells change in the experiment? If yes, which cells underwent the change, and what change occured? If not, explain why there was no change. Some cells of type M underwent the change. They acquired some of the genetic material from the heat- killed BLT cells. In particular, some part of the genetic material they acquired encoded for the gene that was mutated in M. Having received this gene, M cells now behave like the wild-type BLT cells because they can now produce the agent (like the Earth proteins) that restores the wood metabolism pathway. You plan to characterize the alien genetic material. You start by breaking some A . termiticus cells open to determine their molecular composition. You find that they contain various small molecules, carbohydrates, lipids, and two other macromolecules, A and B. In order to determine which macromolecule is the carrier of genetic information, you repeat your previous experiment, but include test tubes where you treat the sample of the heat-killed BLT with either an agent that destroys macromolecule A (A-ase) or macromolecule B (B-ase). You find the following results (including the repeat of your previous experiment in the first 4 lines): Strains and agents Metabolizes wood? BLT Yes Heat-killed BLT No M No Heat-killed BLT +M Yes A-ase treated heat-killed BLT +M Yes B-ase treated heat-killed BLT +M No b) Which molecule is the carrier of genetic information in A. termiticus ? Justify your answer. B is the carrier of genetic information in the alien organism. This is because when the BLT cells are treated with B-ase, no B remains in the sample, and, as a result, no transformation occurs. On the other hand, treatment with A-ase has no bearing on the transformation ability of the heat-killed BLT cells. We, therefore, must conclude that B is the carrier of genetic information. 2
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 9

quiz2_s - MIT Department of Biology 7.014 Introductory...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online