Information for teachers• The tidbit “The Prospect Puppy Burglary” suits nicely as a closure

of lessons about DNA, DNA structure, replication …– Chapter 7 as a preparation supports performance of students

• It is a very active and flexible tidbit• Activities: think and share, clicker questions, gel labeling and final

group discussion.– Potential misconceptions can be corrected, especially with activity # 2

and 4– Homework with different tasks aims higher in Bloom’s taxonomy

• Flexibility: Activity #2 and 4 in particular leave space for discussions and additional questions if you have longer than the planned 20 minutes– #2 and 4 can be assessed as clicker questions in bigger class

room/lecture halls, but also as one-to-one/in pairs with computers in smaller classes, or a group discussion with show of hands/answer cards

• Preparation: colored print-out of worksheet, clickers

CSI New Haven: Canine Special Investigators

The Prospect Puppy Burglary

CSI:NH

The Crime Scene & Suspects

• A prize puppy has been stolen from an apartment on Prospect Hill. The NHPD has arrested three possible suspects after collecting witness statements from the scene:– Suspect A was seen leaving the apartment in the

early morning– Suspect B has been seen taking the dog for a walk

over the last week– Suspect C crashed his/her car while leaving the

parking lot that night

CSI:NH

Your task:

• To use DNA profiling to prepare a police report to convict the thief in court

• You will discuss:– What DNA profiling is– Why & when we use it– Which samples to collect– Which part of DNA is used to differentiate people– Techniques used to examine DNA differences– How to read a DNA profile gel

CSI:NH

What is DNA profiling and how is it useful in the police force? Where else might we employ it?

Write your answer to this question in the space provided on the worksheet

Activity Number 1:CSI:NH

You are the forensic scientist and need to pick a sample to get DNA from. Which sample will you pick?

A – Blood which was on the broken glass of the doorB – Saliva found on a spoon in a coffee mugC – Bunch of hair sticking to broken glass of doorD – Any of the aboveE - Battery cells found in the room

Activity Number 2:CSI:NH

Blood

Red blood cells have no nuclei and so they contain no DNA.

The DNA found when blood is tested comes from the white blood cells.

Using modern techniques, each type of fluid or tissue in the question yields enough usable DNA for testing

Click to continue

CSI:NH

Saliva

Saliva does not contain cells, but as it passes through the salivary ducts, and washes around the mouth, it picks up cells.

Using modern techniques, each type of fluid or tissue yields enough usable DNA for testing

Click to continue

CSI:NH

Hair

Hair does not contain cells, but hair follicles do which can be used for DNA extraction.

Using modern techniques, each type of fluid or tissue yields enough usable DNA for testing

Click to continue

CSI:NH

Any of the above

The DNA found when blood is tested comes from the white blood cells, as red blood cells have no nucleus.

Saliva does not contain cells, but as it passes through the salivary ducts, and washes around the mouth, it picks up cells.

Hair does not contain cells, but hair follicles do which can be used for DNA extraction.

Using modern techniques, each type of fluid or tissue yields enough usable DNA for testing

Click to continue

CSI:NH

Battery cells

Well, try again!

CSI:NH

NHPD Memo - PCR

• To amplify small starting samples of DNA you should use PCR.

• PCR reactions use primers complementary to your sequence of interest to amplify these regions.

• PCR reactions are based on a cycle of these steps:

http://www.biologymad.com/master.html?http://www.biologymad.com/geneticengineering/geneticengineering.htm

CSI:NH

Select the correct sequence to perform your PCR reaction:

A - Select primers, heat, anneal, replicate, extract DNA

B - Select primers, replicate, heat, anneal, extract DNA

C - Extract DNA, select primers, heat, anneal, replicate

D - Extract DNA, select primers, heat, replicate, anneal

CSI:NHActivity Number 3:

That’s not quite right – take another look and try again

CSI:NH

Congratulations, you have amplified your DNA for profiling

• Which regions of DNA will you use to catch the suspect?

A – Single nucleotide polymorphisms (SNPs)B – Short tandem repeats (STRs)C – Chromosome translocationsD – Not sure, let me look in my training manual!

Activity Number 4

CSI:NH

Single nucleotide polymorphisms (SNPs)

SNPs are single base changes that are common throughout the genome

They are inherited and can be used to define people as belonging to certain groups

Click to try again

CSI:NH

Click to continue

CSI:NH

Chromosome translocations

Translocations occur when DNA is copied badly and one arm of a chromosome ends up being switched to another

They are rare events in the genome and often lead to large problems in development

Click to try again

CSI:NH

• You perform gel electrophoresis with the PCR samples from the people from infographic 7.5

• Take one minute to match the labels to the correct part of the gel

CSI:NHActivity Number 5:

A.......... Person 1

Person 2

Person 3

6

4…. repeats

…. repeats

B..........

C..........

Click to continue

CSI:NH

Question: Which label did you put in box C?A - Person 2

B - 6 repeats

C - Person 1

D - 4 repeats

E - Person 3

CSI:NHActivity Number 5:

A.......... Person 1

Person 2

Person 3

6

4

chromosome 7

…. repeats

…. repeats

B..........

C..........

• You have run the gel from the suspects and your supervisor would like you to tell him what you know about the suspects before he reveals who they are – take 5 minutes to discuss the questions on the next slide in a group

• Take notes during your discussion – this will be important for your homework!

Activity Number 6 – name your suspect

blood sample from broken glass at the

crime scene

hair sample from the

crime sceneSuspect A Suspect CSuspect B

DNA from the puppy’s owner

CSI:NH

Who is the puppy thief?

Is one of the suspects related to the puppy’s owner?

What gender do you think each suspect is?

Where might the hair sample have come from?

hair sample from the

crime sceneSuspect A Suspect CSuspect B

DNA from the puppy’s owner

CSI:NH Blood sample from broken glass at the crime scene

Who is the puppy thief?

Is one of the suspects related to the puppy’s owner?Hint – think about how STRs might be inherited from the parents

What gender do you think each suspect is?Hint – think about the sex defining chromosomesWhere might the hair sample have come from?

Blood sample from broken glass at the crime scene

hair sample from the

crime sceneSuspect A Suspect CSuspect B

DNA from the puppy’s owner

CSI:NH

• Write a police report to be presented in court to convict your suspect

• Make sure you include– Why you chose to do DNA profiling

– What experimental steps you took

– Which suspect you think is the thief, and why?

– Explain why you eliminated the other suspects from the investigation

– Is there any doubt in your investigation? How could you make yourself more certain?

CSI:NHHomework activity