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TLS Online TPP Program

#Question id: 4950

Temperature-sensitive (ts) mutations, which are one form of conditional lethal mutation, allow cells to grow at one temperature (for example, 30°C) but not at a higher temperature (for example, 42°C). A large number of temperature-sensitive replication mutants have been isolated in E. coli. These mutant bacteria are defective in DNA replication at 42°C but not at 30°C. If the temperature of the medium is raised from 30°C to 42°C, these mutants stop making DNA in one of two characteristic ways. The “quick-stop” mutants halt DNA synthesis immediately, whereas the “slow-stop” mutants stop DNA synthesis only after many minutes. Extracts from quick-stop mutants halt DNA synthesis immediately at 42°C, whereas extracts from slow-stop mutants do not stop DNA synthesis for several minutes after a shift to 42°C. Suppose extracts from a temperature-sensitive DNA helicase mutant and a temperature-sensitive DNA ligase mutant were mixed together at 42°C. Which of the following statements are correct?

A. The mixed extracts should be fully competent for DNA replication at 30°C; that is, the mixture should exhibit a nonmutant phenotype.

B. The defective DNA helicase extract would provide normal DNA ligase, and the defective DNA ligase extract would provide normal DNA helicase.

C. In practice, the behaviors of extracts from slow-stop mutants and from nonmutant cells are easy to distinguish.

D. Because of the extreme complexity of DNA replication and the large number of proteins involved, cell-free extracts are not capable of maintaining DNA replication indefinitely.

#Unit 3. Fundamental Processes

  1. A & B

  2. B & C

  3. B & D

  4. C & D

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TLS Online TPP Program

#Question id: 17655

#Unit 13. Methods in Biology

In DNA isolation, for protein free solution what will be the ratio at  nm
TLS Online TPP Program

#Question id: 17656

#Unit 7. System Physiology – Animal

The body is too worn down to deal with the stress and leaves the body vulnerable to injury.
TLS Online TPP Program

#Question id: 17657

#Unit 7. System Physiology – Animal

A recent national survey revealed that college students find _____ to be the biggest impediment to their academic success.
TLS Online TPP Program

#Question id: 17658

#Unit 7. System Physiology – Animal

Which of the following is the most accurate description of stress?
TLS Online TPP Program

#Question id: 17659

#Unit 13. Methods in Biology

During your study of the gene for an enzyme you have isolated an amber mutation in the middle of the gene which produces a truncated form of the enzyme. By placing a +1 frameshift mutation a short distance before the amber mutation and a –1 frameshift mutation a short distance after the amber mutation you create a triple mutant that restores expression of a functional, full-length enzyme. 
a) +1 frameshift puts the amber mutation out of frame so that it is no longer read as a stop.
b) -1 frameshift is inserted after the amber so that no longer read as a stop.
c)  -1 frameshift is inserted after the amber to restore the frame of the end of the protein.
d) +1 frameshift puts the amber mutation out of frame so that it restore the frame of the end of the protein.
Which of the following is the correct prediction about the frame shift mutation?
TLS Online TPP Program

#Question id: 17666

#Unit 11. Evolution and Behavior

 In the Mesozoic era, periods included;
A. Cretaceous
B. Jurassic
C. Triassic
i) Increase of dicotyledons
ii) Seeds ferns disappear
iii) Rapid development of angiosperms
iv) Spread of cycads and conifers
v) Gymnosperms declined
Find out the correct match of given period with their plants diversification events;