Year 10 Science · Unit 1 · Lesson 8
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Learning Goals
Read the gel
The diagram below shows a gel electrophoresis result from a crime scene investigation. Lane 1 is the evidence DNA. Lanes 2–5 are four suspects. Smaller fragments are at the bottom (travelled further). Study the band patterns and answer the questions below.
Note: band position represents fragment size. Bands at the same height = same size fragment.
(a) Which suspect's DNA matches the evidence? State which lane and explain how you identified the match.
(b) Suspect A's lawyer argues that because the bands are close together, it could still be a match. Why is this argument scientifically incorrect?
Real-world context
After the 2019–2020 Black Summer bushfires, researchers at the University of the Sunshine Coast used DNA profiling to track individual koalas across south-east Queensland. Hair and scat samples collected from scorched habitat allowed scientists to determine which koalas had survived, estimate population sizes, and identify areas with highest genetic diversity for targeted conservation. This non-invasive technique has been adopted by state and federal wildlife agencies as a standard post-disaster assessment tool.
(a) Explain how DNA profiling can identify an individual koala from a hair or scat sample. In your answer, refer to STRs and why no two koalas share the same profile.
(b) Researchers want to find areas with high genetic diversity for priority conservation. Why is genetic diversity important for the long-term survival of a koala population recovering from a bushfire?
(c) A scientist says: "This technique is better than tagging because it does not disturb the animals." Apart from being non-invasive, give one other advantage of using DNA profiling rather than radio-collar tagging for this koala study.
Wrap Up
In one sentence, describe how gel electrophoresis produces a DNA "fingerprint".