Question

PCR can be used __________. a. to increase the number of specific DNA fragments b. in DNA fingerprinting c. to modify a human genome d. a and b are correct

Short answer

Option d (a and b are correct) is the right answer.

Step-by-step solution

Understanding PCR

Polymerase Chain Reaction (PCR) is a technique used to amplify DNA sequences, generating thousands to millions of copies of a particular DNA segment.

Evaluating Option a

Option a states that PCR can be used "to increase the number of specific DNA fragments." This is a core function of PCR, as it amplifies specific DNA sequences, confirming that this option is correct.

Evaluating Option b

Option b suggests that PCR can be used "in DNA fingerprinting." PCR is indeed a critical technique used in DNA fingerprinting to amplify STRs (Short Tandem Repeats), making this option correct as well.

Evaluating Option c

Option c claims PCR can be used "to modify a human genome." While PCR amplifies DNA, it does not have the functionality to modify or edit genomes; therefore, this option is incorrect.

Conclusion from Evaluations

Since both options a and b are correct, option d "a and b are correct" accurately reflects the use of PCR, whereas option c is incorrect.

Key concepts

DNA Fingerprinting

DNA fingerprinting is a technique that identifies unique patterns within an individual's DNA. This method is widely used in forensic science to solve crimes because each person's DNA is distinct, like a fingerprint.
The process involves collecting samples such as hair, blood, or saliva. Then, specific regions of DNA, known as Short Tandem Repeats (STRs), are amplified using PCR. STRs are repeating sequences in DNA that vary greatly among individuals, making them ideal for identification.
Once the DNA is amplified, it is compared across samples. Scientists pick several STR loci to ensure accuracy, because while one locus might not be unique, the combination of several is.

• High precision in matching DNA profiles.
• Used in legal situations, paternity tests, and identifying remains.

These elements combined ensure that DNA fingerprinting is a powerful tool for identification purposes.

DNA Amplification

DNA amplification refers to the process of making numerous copies of a specific DNA segment. The Polymerase Chain Reaction (PCR) is the most common method for achieving this amplification. PCR's ability to generate millions of copies from a tiny DNA sample is revolutionary, particularly in fields like medical diagnostics and biotechnology.
To perform PCR, scientists need a DNA template, nucleotides, primers, and a DNA polymerase enzyme. During the PCR, the DNA first denatures, separating into two strands. Primers then attach to the targeted DNA regions, and the DNA polymerase extends the strand, creating a new double-stranded DNA.

• Repeated cycles rapidly increase the number of DNA copies.
• Essential for processes requiring abundant DNA, such as sequencing.

This capability allows minor samples to be analyzed, making PCR indispensable in many scientific areas.

Genome Editing Limitations

Unlike PCR, genome editing actively alters DNA sequences in an organism's genome. However, current technologies face significant limitations which prevent complete precision in editing. While tools like CRISPR-Cas9 can add, remove, or change DNA bases, errors can occur.
These inaccuracies arise from off-target effects, where unintended regions of the DNA are altered. Ensuring only the desired part of the genome is edited requires rigorous testing and checking.

• Possibility of unintended mutations.
• Potential ethical concerns surrounding genome modification.

Moreover, the long-term effects of genome editing are still largely unknown, with ethical debates around human genome editing posing further challenges. It is a complex yet promising area requiring careful consideration and regulation.