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TLS Online TPP Program

#Question id: 757

_______________ a bacterial enzyme, uses the energy of ATP hydrolysis to introduce negative supercoiling into DNA hence removing positive supercoiling generated during replication.

#SCPH01 Biochemistry

  1. nucleases

  2.  DNA polymerases

  3.  helicases

  4.  DNA gyrase

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#Question id: 5526

#SCPH01 Biochemistry

The allantois
TLS Online TPP Program

#Question id: 15657

#SCPH01 Biochemistry

You are studying a new strain of E. coli that can utilize the disaccharide melibiose very efficiently. You find that utilization depends on the enzyme melibiase, which is encoded by the gene Mel1. Mel1 is not expressed unless melibiose is present in the growth medium.
You next construct a MelA– MelB– double mutant, which gives the following behavior:
 
Which of your two models is consistent with this new data?
a) the MelA- MelB- double mutant is identical to the MelB- mutant
b) MelA- is epistatic to MelB-
c) MelB- is epistatic to MelA-
d) the MelA- MelB- double mutant is identical to the MelA- mutant
Which of the following is the correct prediction about the double mutants?
TLS Online TPP Program

#Question id: 12578

#SCPH06 I Botany

Refer to the following experiment, which is designed to test the co evolutionary relationships among an unpalatable butterfly (the  monarch),  a  palatable  butterfly  (the  viceroy),  and  a  butterfly  predator  (the  jay).  Monarch butterflies are reared on three diets: milkweed (their natural food), cabbage, and cabbage treated with an extract from milkweed leaves. Viceroy butterflies, mimics of monarchs, also are reared on three diets: willows (their natural food), cabbage, and cabbage treated with an extract from milkweed leaves. In trial 1 of the first experiment, adult butterflies reared on a particular diet are presented one at a  time  at  1-hour  intervals  to  jays  and  the  jays  are  allowed  to  feed.  Each jay is  fed  until  it refuses to eat the butterfly presented, but no more than 12 butterflies are presented to a jay during a particular test. Five birds are used for each test; therefore, up to 60 butterflies can be consumed for each diet test. The observer records the actual number of butterflies  eaten. In trial 2, the experiment is repeated 2 weeks later. In the second experiment, the butterflies are reared on the same diets as in experiment 1. However, when they are offered to jays, some jays receive a monarch  reared  on  milkweed  before  being  offered  the  butterflies  reared  on  the  experimental  diets;  the  other  group  of jays is  first given a viceroy reared on willow before being  offered the butterflies reared on the experimental diets. The initial butterfly offered is included in the total number eaten, but no more than 12 butterflies are presented to each jay

Which of the following supports the hypothesis that viceroys receive protection from predation because they resemble monarchs?
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#Question id: 4342

#SCPH01 Biochemistry

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If a researcher moves the operator to the far end of the operon, past the transacetylase (lacA) gene, which of the following processes would likely occur when the cell is exposed to lactose?
TLS Online TPP Program

#Question id: 11658

#SCPH28 | Zoology

Directional community changes due to the cause of succession, factors involve such as