explain why the answer is e? In 1968, Tsuneko and Reiji Okazaki studied with Bac
ID: 208913 • Letter: E
Question
explain why the answer is e?
In 1968, Tsuneko and Reiji Okazaki studied with Bacteriophage T4 that produce temperature-sensitive DNA ligase (25°C permissive & 37°C nonpermissive). Examination of DNA replication in extracts of E. coli infected with this temperature sensitive T4 mutant the presence of [3H]-thymidine in the mutant would show which of the following?
The accumulation of short segments of unlabeled DNA at 25°C but not at 37°C.
The incorporation of short fragments of radioactive DNA into longer ones at 25°C and at 37°C.
The accumulation of short segments of radioactive DNA at 25°C but not at 37°C.
The accumulation of short segments of unlabeled DNA at 25°C and at 37°C.
The accumulation of short segments of radioactive DNA at 37°C but not as 25°C.
Explanation / Answer
The answer would be E, because the scientist wanted to show the example of discontinuous replication via okazaki fragments formation as we now know in case of lagging strand DNA synthesis. With this experiment they gave the hypothesis that if discontinuous replication occurs involving short DNA chains linked by polynucleotide ligases then the newly synthesized short DNA chains would accumlate in the cells under the condition where the activity of the T4 ligase would be temporarily impaired.
Now if the function of the T4 ligase is impaired then it means that it will not work and that is why we will not see the short segments at 25°c but at 37°c. And the fact that radioactive thymidine was used so that is why the DNA segments would be radioactive.
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