Which of the following best states the overall goal of the polymerase chain reaction (PCR) process?

• A. To sequence the entire genome of an organism
• B. To separate DNA fragments based on their size using an electric field
• C. To synthesize proteins from mRNA templates
• D. To amplify a specific segment of DNA, generating millions of copies from a small initial sample

Answer: (D)

Verified step by step guidance

1. Understand the purpose of PCR: The polymerase chain reaction (PCR) is a molecular biology technique used to amplify a specific segment of DNA, creating millions of copies from a small initial sample. This is useful for applications such as genetic testing, forensic analysis, and research.
2. Clarify why the other options are incorrect: Sequencing the entire genome of an organism involves techniques like next-generation sequencing, not PCR. Separating DNA fragments based on size is done using gel electrophoresis, not PCR. Synthesizing proteins from mRNA templates is the role of translation, not PCR.
3. Identify the key components of PCR: PCR requires a DNA template, primers (short DNA sequences that bind to the target region), DNA polymerase (enzyme that synthesizes new DNA strands), nucleotides (building blocks of DNA), and a thermal cycler to control temperature changes.
4. Break down the PCR process: PCR involves three main steps repeated in cycles: (1) Denaturation: Heating the DNA to separate its strands, (2) Annealing: Cooling to allow primers to bind to the target DNA sequence, and (3) Extension: DNA polymerase synthesizes new DNA strands by adding nucleotides complementary to the template.
5. Summarize the goal: The overall goal of PCR is to amplify a specific DNA segment, generating millions of copies from a small initial sample, which is essential for various biological and medical applications.