PCR can be used to identify an unknown bacterium because
a. DNA can be electrophoresed.
b. the DNA primer is specific to particular target.
c. DNA sequences.
d. DNA polymerase will replicate any bacterial DNA.
e. all cells have RNA.
f. all cells have DNA.
The Correct Answer and Explanation is:
Correct Answer:
PCR can be used to identify an unknown bacterium because it amplifies specific DNA sequences unique to that organism.
Explanation (300+ words):
Polymerase Chain Reaction (PCR) is a powerful molecular biology technique that allows for the amplification of specific DNA sequences. This process can generate millions of copies of a particular DNA fragment from a tiny initial sample. When identifying an unknown bacterium, PCR is highly valuable because each species of bacteria has unique genetic sequences in its DNA, particularly in conserved regions such as the 16S ribosomal RNA gene.
The 16S rRNA gene is present in all bacteria but contains both conserved and variable regions. The conserved regions allow for the binding of universal primers—short DNA sequences used to start the DNA replication process in PCR—while the variable regions differ between species. By designing primers that target the conserved regions flanking the variable regions, scientists can amplify the 16S rRNA gene from any bacterial sample. Once amplified, the DNA sequence of the product can be analyzed through a process called sequencing. The resulting sequence can then be compared to a database of known bacterial 16S rRNA sequences to identify the unknown organism.
This method is particularly useful when:
- The bacterium is difficult to culture using traditional methods.
- The bacterial sample is part of a complex mixture (e.g., in environmental or clinical samples).
- Rapid and specific identification is required.
In addition to 16S rRNA, other genes specific to bacterial pathogens (e.g., toxin genes or antibiotic resistance genes) can also be targeted with PCR to provide further characterization.
PCR offers high sensitivity and specificity, meaning it can detect even small amounts of bacterial DNA and accurately identify the bacterium based on its genetic material. Because DNA is more stable and unique than proteins or other cell components, PCR provides a reliable and rapid tool for bacterial identification in clinical diagnostics, research, and environmental monitoring.