Free PCR Sample Preparation & Nucleic Acid Extraction Questions and Answers

Question 1

What is the goal of nucleic acid extraction?

Accepted Answer

To isolate DNA or RNA from samples

Answer

The goal of nucleic acid extraction is to isolate and purify DNA or RNA from biological samples. This process separates the nucleic acids from other cellular components like proteins, lipids, and carbohydrates, which can interfere with downstream molecular applications. Obtaining a clean, high-quality sample is essential for accurate results in techniques such as PCR, sequencing, or cloning.

Question 2

Why must samples be free of contaminants before PCR?

Accepted Answer

They can inhibit enzyme activity

Answer

Samples must be free of contaminants before PCR because various substances can inhibit enzyme activity. Contaminants like proteins, salts, or other cellular debris can interfere with the Taq polymerase, preventing efficient DNA amplification. Ensuring a clean sample is crucial for obtaining reliable, specific, and accurate PCR results, avoiding false negatives or reduced yield.

Question 3

Which chemical helps lyse cells during DNA extraction?

Accepted Answer

Detergent (SDS)

Answer

Detergents, such as SDS (Sodium Dodecyl Sulfate), are commonly used in DNA extraction to help lyse cells. They disrupt the lipid bilayers of cell membranes and nuclear envelopes, effectively breaking open the cells and releasing their contents, including DNA. This initial lysis step is critical for making the DNA accessible for subsequent purification steps.

Question 4

What is the purpose of using proteinase K in DNA extraction?

Accepted Answer

Degrades proteins in the sample

Answer

Proteinase K is an enzyme used in DNA extraction to degrade proteins present in the sample. Its primary purpose is to break down cellular proteins, including nucleases that could degrade DNA, and histones that are tightly bound to DNA. This enzymatic digestion helps to purify the DNA by removing protein contaminants, ensuring a cleaner and more stable DNA sample.

Question 5

What role does ethanol play in DNA extraction?

Accepted Answer

Precipitates and isolates DNA

Answer

Ethanol plays a crucial role in DNA extraction by precipitating and isolating DNA from the aqueous solution. When added to the DNA solution, it reduces the solubility of DNA, causing it to clump together and become visible. This allows the DNA to be easily pelleted by centrifugation, separating it from soluble contaminants and facilitating its purification.

PCR - Polymerase Chain Reaction Certification Practice Test

PCR - Polymerase Chain Reaction Certification Practice Test

Free PCR Sample Preparation & Nucleic Acid Extraction Questions and Answers