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Question Video: Defining the Term Oligonucleotide Biology

In the process used by gene machines, oligonucleotides are formed. What is an oligonucleotide?

02:45

Video Transcript

In the process used by gene machines, oligonucleotides are formed. What is an oligonucleotide? (A) A strand of DNA formed from a strand of mRNA, catalyzed by reverse transcriptase. (B) A sequence of amino acids that code for the desired gene. (C) A naturally occurring section of DNA. (D) A synthetically produced short strand of DNA or RNA. Or (E) a section of DNA removed from a genome by restriction enzymes.

In this question, we’re being asked about oligonucleotides, which are involved in the process used by gene machines to synthesize genes. Let’s quickly review the concepts behind gene machines.

A gene machine is used to synthesize a gene. A gene is a stretch of DNA nucleotides whose sequence forms the code required to synthesize a specific functional unit, like a protein.

You might remember learning about the central dogma of molecular biology, which states how DNA is transcribed into mRNA, which is then translated into an amino acid sequence that forms a protein. In order to synthesize a gene for a particular protein, a gene machine must be provided with the sequence of nucleotides needed. In order to synthesize a gene with the required sequence, the gene machine uses short sequences called oligonucleotides. An oligonucleotide is a synthetically produced single-stranded stretch of DNA or RNA. The word part oligo- is the Greek word that means few, emphasizing that this strand is only made up of a few nucleotides.

Let’s say our gene machine is being used to synthesize a gene that should look like this. The gene machine will use two oligonucleotides to begin the synthesis process. One might look something like this. The other might look like this. As you can see, the two oligonucleotides are chosen so that they provide an overlapping region of double-stranded DNA, as well as two single-stranded overhangs. The gene machine can then use an enzyme called Taq polymerase to fill in the gaps and synthesize the complete sequence.

Let’s see if we can have a go at filling in the sequence the way Taq polymerase would. If we begin with the upper strand, we can use the nucleotide sequence from the lower strand to figure out the complementary nucleotides needed. Similarly, we can fill in the lower strand by using the complementary nucleotides of the upper strand. Now we have the complete double-stranded DNA sequence that makes up the gene. We can use what we’ve learned about gene machines and oligonucleotides to answer our question. An oligonucleotide would be best described as (D): a synthetically produced short strand of DNA or RNA.

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