Outline the typical workflow for generating DNA evidence from a crime scene, including sample handling and analysis.

Outline the typical workflow for generating DNA evidence from a crime scene, including sample handling and analysis.

• A. Collect and preserve evidence with chain of custody; extract DNA; quantify; PCR amplify STRs; separate by capillary electrophoresis; compare profiles with reference data; interpret.
• B. Immediately sequence the entire genome and compare.
• C. Only collect blood type information.
• D. Ignore chain of custody.

Answer: (A)

The main idea is to follow a careful, end-to-end process that preserves evidence quality while turning it into a usable DNA profile. Start with collecting and preserving the evidence under a documented chain of custody, using proper packaging and labeling to prevent contamination and to track every transfer. In the lab, extract the DNA, then quantify how much DNA is present and check for inhibitors that could affect analysis. Then PCR amplify a standard set of STR loci, because these short, repetitive DNA regions differ greatly between individuals and produce highly distinguishing profiles. The amplified fragments are separated by capillary electrophoresis, producing a readable DNA profile of allele sizes. This profile is compared to reference data from a known person or a database to determine a match or exclusion, and the results are interpreted in a statistical context. Whole-genome sequencing of the whole sample isn’t the routine workflow due to cost and data complexity, and collecting only blood type information lacks sufficient discriminatory power. Ignoring chain of custody would make the evidence invalid for legal use.

The main idea is to follow a careful, end-to-end process that preserves evidence quality while turning it into a usable DNA profile. Start with collecting and preserving the evidence under a documented chain of custody, using proper packaging and labeling to prevent contamination and to track every transfer. In the lab, extract the DNA, then quantify how much DNA is present and check for inhibitors that could affect analysis. Then PCR amplify a standard set of STR loci, because these short, repetitive DNA regions differ greatly between individuals and produce highly distinguishing profiles. The amplified fragments are separated by capillary electrophoresis, producing a readable DNA profile of allele sizes. This profile is compared to reference data from a known person or a database to determine a match or exclusion, and the results are interpreted in a statistical context. Whole-genome sequencing of the whole sample isn’t the routine workflow due to cost and data complexity, and collecting only blood type information lacks sufficient discriminatory power. Ignoring chain of custody would make the evidence invalid for legal use.