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iGenetics 3rd Edition by Peter Russell
Edition 3ISBN: 978-0321569769iGenetics 3rd Edition by Peter Russell
Edition 3ISBN: 978-0321569769 Exercise 1
Griffith's experiment injecting a mixture of dead and live bacteria into mice demonstrated that (choose the correct answer) a. DNA is double-stranded.
B) mRNA of eukaryotes differs from mRNA of prokaryotes.
C) a factor was capable of transforming one bacterial cell type to another.
D) bacteria can recover from heat treatment if live helper cells are present.
B) mRNA of eukaryotes differs from mRNA of prokaryotes.
C) a factor was capable of transforming one bacterial cell type to another.
D) bacteria can recover from heat treatment if live helper cells are present.
Explanation
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In 1928, a British medical officer by the name of Frederick Griffith conducted an experiment using live and dead bacteria. He used two strains of Streptococcus pneumonia , the R strain and the S strain. The R strain is rough and nonvirulent, while the S strain is smooth and virulent. In order to further facilitate his experiment, Griffith used two different types of the bacteria, those with type II coats and those with type III coats.
Thus, Griffith used Type IIR and Type IIIS bacteria. Since bacteria can mutate, it is possible for R bacteria to mutate into S and vice versa; however, there is no mutation between types. Type IIR bacteria can mutate into Type IIS bacteria but not into any Type III bacteria. Similarly, Type IIIR bacteria can mutate into type IIIS bacteria but not into any type II bacteria.
Griffith injected combinations of the living and dead bacteria in to mice. When Griffith injected Type IIR bacteria in to the mice, the mice survived with no bacteria present in their bloodstream. When Griffith injected Type IIIS bacteria in to mice, the mice died with virulent bacteria found in their bloodstream. When Griffith injected heat-killed Type IIIS bacteria in to mice, the mice survived with no bacteria present in their bloodstream. Finally, when Griffith injected Type IIR bacteria and heat killed Type IIIS bacteria into mice, the mice died with Type IIIS bacteria found in their bloodstream.
Since, in the last experiment, Griffith knew that Type IIR bacteria cannot mutate in to Type IIIS bacteria, he concluded that some of the Type IIR bacteria had been transformed into Type IIIS bacteria via interaction between the dead and live cells.
Choice (a) is incorrect because the experimental results do not indicate whether or not the genetic material is deoxyribonucleic acid (DNA) or protein. So, it does not indicate that the DNA is double stranded. In fact, Griffith believed that protein acted as the genetic material, not DNA.
Thus, choice (a) is incorrect.
Choice (b) is incorrect because Griffith's experiment is not at all about messenger ribonucleic acid (mRNA). Griffith's experiment is about how genetic information is passed between bacterial strains, which are prokaryotes.
Thus, choice (b) is incorrect.
Choice (d) is incorrect because there is no such thing as helper cells for bacteria. Additionally, bacteria cannot recover from heat treatment but they can transfer their DNA to other strains.
Thus, choice (d) is incorrect.
Choice (c) is correct because Griffith did show that there is a factor that transforms one bacterial cell type into another.
Hence, the correct answer is:
(c) a factor was capable of transforming one bacterial cell type to another.
Thus, Griffith used Type IIR and Type IIIS bacteria. Since bacteria can mutate, it is possible for R bacteria to mutate into S and vice versa; however, there is no mutation between types. Type IIR bacteria can mutate into Type IIS bacteria but not into any Type III bacteria. Similarly, Type IIIR bacteria can mutate into type IIIS bacteria but not into any type II bacteria.
Griffith injected combinations of the living and dead bacteria in to mice. When Griffith injected Type IIR bacteria in to the mice, the mice survived with no bacteria present in their bloodstream. When Griffith injected Type IIIS bacteria in to mice, the mice died with virulent bacteria found in their bloodstream. When Griffith injected heat-killed Type IIIS bacteria in to mice, the mice survived with no bacteria present in their bloodstream. Finally, when Griffith injected Type IIR bacteria and heat killed Type IIIS bacteria into mice, the mice died with Type IIIS bacteria found in their bloodstream.
Since, in the last experiment, Griffith knew that Type IIR bacteria cannot mutate in to Type IIIS bacteria, he concluded that some of the Type IIR bacteria had been transformed into Type IIIS bacteria via interaction between the dead and live cells.
Choice (a) is incorrect because the experimental results do not indicate whether or not the genetic material is deoxyribonucleic acid (DNA) or protein. So, it does not indicate that the DNA is double stranded. In fact, Griffith believed that protein acted as the genetic material, not DNA.
Thus, choice (a) is incorrect.
Choice (b) is incorrect because Griffith's experiment is not at all about messenger ribonucleic acid (mRNA). Griffith's experiment is about how genetic information is passed between bacterial strains, which are prokaryotes.
Thus, choice (b) is incorrect.
Choice (d) is incorrect because there is no such thing as helper cells for bacteria. Additionally, bacteria cannot recover from heat treatment but they can transfer their DNA to other strains.
Thus, choice (d) is incorrect.
Choice (c) is correct because Griffith did show that there is a factor that transforms one bacterial cell type into another.
Hence, the correct answer is:
(c) a factor was capable of transforming one bacterial cell type to another.
iGenetics 3rd Edition by Peter Russell
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