DNA Analysis Techniques Flashcards

What is Polymerase Chain Reaction (PCR) used for in DNA analysis?

Answer: To amplify DNA segments

Polymerase Chain Reaction (PCR) is a fundamental technique in DNA analysis used to amplify specific segments of DNA, creating millions of copies from even a tiny sample. This amplification is crucial in forensic science because crime scene evidence often contains only minute amounts of DNA, which would otherwise be insufficient for further analysis. PCR enables the generation of enough material for techniques like STR profiling.

What technique separates DNA fragments based on size?

Answer: Gel electrophoresis

Gel electrophoresis is a laboratory technique that separates DNA fragments based on their size and electrical charge. DNA fragments, being negatively charged, migrate through a gel matrix towards a positive electrode when an electric current is applied. Smaller fragments move faster and further through the gel than larger ones, allowing for their effective separation and visualization, which is crucial for DNA profiling.

What is the purpose of DNA extraction in forensic analysis?

Answer: Isolate DNA from cells

The purpose of DNA extraction in forensic analysis is to isolate and purify DNA from other cellular components, such as proteins, lipids, and carbohydrates, found in biological samples. This crucial initial step makes the DNA accessible for subsequent analytical techniques like PCR and STR analysis. Proper extraction is essential to remove contaminants that could interfere with downstream reactions and lead to inaccurate results.

What is Short Tandem Repeat (STR) analysis?

Answer: Examining repeated DNA sequences

Short Tandem Repeat (STR) analysis is a widely used forensic technique that examines specific regions of DNA containing short, repeating nucleotide sequences. Individuals inherit a unique number of these repeats from each parent, creating a highly variable and distinctive genetic profile. By analyzing multiple STR loci, forensic scientists can generate a unique DNA profile for individual identification, crucial for linking suspects to crime scenes.

What is the role of a DNA sequencer?

Answer: Determine nucleotide order

The primary role of a DNA sequencer is to determine the precise order of nucleotides (adenine, guanine, cytosine, and thymine) within a DNA molecule. While other techniques amplify or separate DNA, sequencing provides the exact genetic code. This detailed information is essential for advanced genetic analysis, identifying specific mutations, or confirming the identity of a DNA sample with high precision.

What is mitochondrial DNA analysis used for?

Answer: Analyze maternally inherited DNA

Mitochondrial DNA (mtDNA) analysis is used to analyze maternally inherited DNA, as mitochondria are passed down exclusively from the mother to her offspring. This technique is particularly valuable in forensic cases where nuclear DNA is degraded or scarce, such as in old bones, hair shafts without roots, or highly degraded samples. It can establish maternal lineage connections, even across generations, when traditional nuclear DNA analysis is not feasible.

Why is contamination prevention critical in DNA analysis?

Answer: Avoid false results

Contamination prevention is critically important in DNA analysis to avoid false or misleading results. Even minute amounts of foreign DNA from sources like lab personnel or other samples can mix with the evidence DNA, leading to an incorrect genetic profile. Strict protocols, sterile equipment, and dedicated workspaces are essential to maintain sample integrity and ensure accurate and reliable forensic conclusions.

What does quantitation measure in DNA testing?

Answer: DNA quantity

Quantitation in DNA testing measures the precise amount of human DNA present in a forensic sample. This step is crucial because downstream applications, such as PCR amplification, require a specific amount of DNA for optimal performance. Knowing the DNA quantity helps determine the appropriate amount of sample to use, ensuring successful amplification and preventing issues like inhibition or overloading of reactions.

What is capillary electrophoresis used for in DNA analysis?

Answer: Separate DNA fragments by size

Capillary electrophoresis (CE) is a high-resolution technique used in DNA analysis to separate DNA fragments by size, particularly those generated during STR analysis. It works by applying an electric field across a narrow capillary filled with a polymer, causing DNA fragments to migrate and separate based on their size. CE offers greater speed, automation, and resolution compared to traditional gel electrophoresis, making it ideal for high-throughput forensic applications.