Teaching sequence

Work through this resource material in the following sequence:

5 minutes - Activating prior knowledge (optional)
10 minutes – Tune in: What is DNA and what does it do?
20 minutes – Find out: How is DNA used in forensic science?
20/25 minutes – Take action: Who stole the exam papers?
5 minutes – Reflection

Optional: Activating prior knowledge

If completing these lessons in sequence, invite students to reflect on what they remember from the last lesson by writing one thing from the last lesson on a post-it note and adding it to the board

Hint: You could also use an app like Padlet (padlet.com) to complete this. You can then discuss the responses and fill in the memory gaps.

Tune in: What is DNA and what does it do?

Note: If the students haven’t yet learnt about DNA in science, you may need to spend more time on Part A and do some DNA modelling or other activities. The Biology Corner and the Gene Technology Access Centre websites are good places to look for helpful resources.

Step 1.

Think, pair, share the question “What is DNA and what does it do?”.

Step 2.

Show the following video to elaborate further on DNA:

What is DNA and How Does it Work? - Stated Clearly (https://youtu.be/zwibgNGe4aY)

Step 3.

Discuss as a class how DNA could be used as evidence in Forensic Science.

Hint: Again, apps like Padlet (padlet.com) can be used as a way of allowing students to brainstorm.

Find out: How is DNA used in forensic science?

Step 1.

Rewatch the relevant part of the following video from the Sci Show on Youtube:

The Real Science of Forensics - Sci Show (https://youtu.be/h3-Pj-zbEq8?t=468) (7.46 mins - 8.50 mins)

Step 2.

Ask the students what questions they have about the information given and record those questions on the board.

Step 3.

Watch the following video:

Inside the Crime Lab: Forensic Biology DNA Unit - Denver Police (https://youtu.be/kF6EGa8GpD0)

Step 4.

Discuss as a class any of the questions from the board that the video answered. Record any new questions the students may now have.

Step 5.

Ask the students what they noticed about the scientists working in the clip and what they were wearing (i.e. gloves, face masks, etc). Discuss why the scientists are wearing these things (i.e. to reduce contamination of the samples with their own DNA). Discuss what that might mean for forensic scientists working at the actual crime scene.

Take action: Who stole the exam papers?

Step 1.

Watch the following clip from Oxford Education on Youtube:

How is DNA fingerprinting used to identify a criminal? - Oxford Education (https://youtu.be/AkBUriMK9u8)

Step 2.

Explain that the process used in the previous clip to separate the DNA fragments is called gel electrophoresis. Scientists use electrophoresis to analyse the STRs in the DNA described in the first clip of this lesson.

Step 3.

Ask students to form small groups and provide each group with the DNA Profiling Worksheet. Using the ‘Who stole the exam papers?’ scenario, invite them to role-play analysing DNA evidence to solve a crime.

Reflection

Invite students to complete the following 3:2:1 reflection:

3 pieces of evidence DNA can be obtained from
2 ways DNA evidence can be contaminated
1 question you have about using DNA evidence.

Differentiated learning

Extension - Students could research real cases where suspects were convicted or acquitted on DNA-based evidence and present their findings to the class. The DNA profiling video in the Forensic Science section of Secrets of the Sequence is a good place to start.

Hint: press the mp4 button.

If the students are interested (or it fits into what you are wanting to teach), you could watch the following clip about the polymerase chain reaction process to explain why the samples are amplified (i.e. due to small amounts of DNA that can’t be analysed) and how it is done (i.e. Polymerase Chain Reaction or PCR).

What is Polymerase Chain Reaction? | PCR Explained - 2 Minute Classroom (https://youtu.be/hO3mTqrEeq8)

Provisions for Learning Support - Group students in a way that allows peer support where needed. For example, you may wish to pair students who have challenges in following a series of discrete instructions with a student who will support their partner, as well as providing a written set of instructions for all students to follow.

Real-life CSI - Cracking the Case with the Code

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