Q9 - SalI/XhoI Restriction Cloning Analysis

Theoretical 1 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

Recombinant DNA & Biotechnology Techniques

Some restriction enzymes have different recognition sequences but create the same sticky ends, as shown below for SalI and XhoI. The following gel electrophoresis image shows linearized DNAs obtained after complete restriction enzyme digestion of non-recombinant (empty vector) and recombinant (containing gene X) expression plasmid vectors. The expression vector includes a strong promoter near its cloning site. The insert of the recombinant plasmid was a product of SalI digestion. The insert was ligated into the vector which had been cut with XhoI.

All recombinant vectors gave the same pattern in the gel

Figure 1. Figure 1.

Figure 2. Figure 2.

Using the information and data, determine which of the statements are true or which are false.

A. The data indicate that two copies of the insert were cloned in the expression vector.

B. Half of the clones are expected to be able to transcribe the mRNA of gene X.

C. An XhoI site exists outside of the insert in the recombinant vector of the experiment.

D. The 2 kb fragment seen in the gel can be used as probe to screen for the recombinant vectors

E. If the insert produced by SalI digestion was ligated into a vector that had been cut with both XhoI and SalI enzymes and the recombinant plasmid subsequently cut with XhoI, a 4 kb product would be obtained.

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Question reproduced from IBO 2018, Theoretical Paper 1, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)