Video Transcript
In the process of forming recombinant DNA, why is it important that both the desired
section of DNA and the bacterial plasmid are cut using the same restriction
enzyme? (A) To reduce the likelihood of the bacterial cell rejecting the DNA. (B) To ensure the DNA and plasmid are the same size. (C) To leave noncomplementary blunt ends. (D) To leave complementary sticky ends. (E) To save money.
Recombinant DNA is the combination of DNA coming from the genomes of at least two
different types of organism. The DNA molecules are brought together by laboratory techniques. This creates a new genetic sequence that would not be naturally found in a
genome. Typically, in the process of forming recombinant DNA, a desired DNA sequence is
extracted from the genome of an organism.
Let’s imagine that the fluorescent protein produced by this jellyfish is our gene of
interest. To extract this gene, we can use a restriction enzyme, which is an enzyme that
cleaves DNA at specific recognition sites. When cutting DNA at their recognition sites, some restriction enzymes are able to
leave a single-stranded overhang at each extremity of the gene of interest. These ends are called sticky ends.
By using the same enzyme to cut the bacterial plasmid where the gene of interest
needs to be inserted, complementary sticky ends will be created at the extremities
of the plasmid. Due to the complementarity of these sticky ends, the two DNA fragments can stick to
one another. After ligation by a DNA ligase, we obtain a recombinant DNA.
In our example, the gene of a jellyfish is inserted into the plasmid of a
bacteria. If the gene of interest in the plasmid had been cut with different restriction
enzymes, the sticky ends would not be complementary. This would prevent the formation of a recombinant DNA.
We can now select (D) as the right answer. It’s important that both the desired section of DNA and the bacterial plasmid are cut
using the same restriction enzymes to leave complementary sticky ends.
