Objective: SWBAT explain how crime scene evidence is processed to obtain DNA.

Do Now:1.So far we have completed two DNA extraction

(banana and human). We used spoons, cups and toothpicks in both labs. List 3 more materials that we used in BOTH labs.

2.Using your DNA molecule that we build, label two nucleotides, 4 nitrogen bases and the backbone of DNA.

3.Name the two functions of DNA.

Lab

Why did we use soap?Why did we use salt?Why did we stir for ten minutes?Why did we use alcohol?

Weak bondDNA does not dissolve alcohol pulls the DNA out and separates it

Materials

• Soap- breaks down the membranes to expose DNA

• Salt – breakdown proteins to release DNA To clump DNA together

• Stir- break down both membranes, breakdown proteins, to make DNA salty

• Alcohol- separates and clumps DNA

Now that you've successfully extracted DNA from one source, you're ready to experiment further. Try these ideas or some of your own:

Experiment with other DNA sources. Which source gives you the most DNA?

Experiment with different soaps and detergents. Do powdered soaps work as well as liquid detergents? How about shampoo or body scrub?

Experiment with leaving out or changing steps. We've told you that you need each step, but is this true? Find out for yourself. Try leaving out a step or changing how much of each ingredient you use.

Which organisms produce the most DNA? Try extracting DNA from other things that you think might have DNA.

Why do scientist use these materials to extract DNA?

• Variable

Fruit Vegetable

Liquid soap powdered soap, shampoo

Salt Vinegar

Where can DNA evidence be found?

BS Burst• Blood• Semen• Bone• Urine• Saliva• Tooth

Collected with?

Gloves Tweezers Swab

Blood Blood Blood

Semen Semen Semen

Bone Bone

Urine Urine Urine

Root of Hair Root of Hair

Saliva

Tooth Tooth

Let dry and collect in paper bag

How do you let it dry?

Why collect it in paper bag and not plastic?

~Moisture

Every living thing has

DNA.

That means that you have

something in common with a zebra, a tree, a

mushroom and a beetle!!!!

DIRECTIONS:

1) Color the individual structures on the worksheet as follows:adenine = red thymine = greenguanine = blue cytosine = yellowphosphate = brown deoxyribose = purple2) Cut out each structure.3) Using the small symbols (squares, circles and stars) on the structures as guides, line up the bases, phosphates and sugars.4) Glue or tape the appropriate pairs together to form nucleotides.

Exit Ticket

1. The bond that holds the nitrogen bases together is calleda. Nitrogen bondb. Hydrogen bondc. Sugar bondd. Toothpick bond

2. Where is DNA found on a crime scene?

3. How is DNA collected from a scene?

DNA is like a fingerprint because everyone’s is a little

different!

You can tell people apart by their fingerprints………

and their DNA!

Why does variations in nitrogen base sequences aids in the distinctiveness of an individual?

How does the nitrogen base structure provide an identifying characteristic to DNA?

The sequencing (order) of the bases provides a code (instructions) to make a certain proteins.

For example:

Lab

Why did we use soap?Why did we use salt?Why did we stir for ten minutes?Why did we use alcohol?

DNA does not dissolve alcohol pulls the DNA out and separates its

Post Lab Questions(to be written in your books)

DNA stands for _________________. The DNA is found on the ______ which is found in the nucleus of cells. The backbone of DNA is made up of alternating _______ and _______ groups. The ____ on my model represents the backbone of DNA. The 4 nitrogen bases are ______, ________, __________, and ______. The _______ on my model represents the nitrogen bases. Adenine always pairs with _______. ________ always pairs with _________. The nitrogen bases are held together by a weak _____ bond. The three molecules that make up a nucleotide are _______, ________, and ________.

Exit ticket

1. Name the four bases that pair together DNA?2. The backbone of DNA is made up of what

two molecules?3. What are the two functions of DNA?

Within cells, DNA is organized into structures called chromosomes.

DNA Molecule

These chromosomes are duplicated before cells divide, in a process called DNA replication.

The backbone of the DNA strand is made from alternating phosphate and sugar residues.

DNA Molecule

Genomic DNA is located in the cell nucleus of eukaryotes, as well as small amounts in mitochondria and chloroplasts. In prokaryotes, the DNA is held within an irregularly shaped body in the cytoplasm called the nucleoid.

The genetic information in a genome is held within genes, and the complete set of this information in an organism is called its genotype.

DNA Molecule

A gene is a unit of heredity and is a region of DNA that influences a particular characteristic in an organism.

Soooo…. How do we tell people apart just by their DNA

anyways???

We are ALL a little bit different!

Along with the meaningful DNA that encodes for physical traits, we have a lot of "junk DNA."

Strings of repeating patterns and filler material.  STR stands for short terminal repeating sections, and this area of DNA represents a pattern, 2 to 7 letters long that repeats itself many times.  How many times varies between people. 

This process is called genetic fingerprinting, or more accurately, DNA profiling.

Suspect #1 DNA sample

Our DNA has different sizes of pieces so it makes a different pattern when it’s all

cut up.Suspect #2 DNA sample

In DNA profiling, the lengths of variable sections of repetitive DNA, such as short tandem repeats, are compared between people. This method is usually an extremely reliable technique for identifying a criminal

                         

                         

This is what it really looks like!!!

Suspect #1 Suspect #2

Genetic fingerprinting is used in forensic science, to match suspects to samples of blood, hair, saliva or semen.

Can you guess which one is Sara and which one is Miss Ellis?

Which suspects DNA sample is the red box around?

?Suspect #1 Suspect #2

Now let’s solve a mystery using DNA

clues!(Just like they do on CSI!!!)

Miss Maize was returning from a shopping trip to the market, arms filled with groceries when a young man stopped her to ask for directions. She put down her groceries and was helping the man when another person snatched her bags from right beside her. She didn’t see the person’s face but managed to grab hold of his arm for a second and scratched his skin.

• Full name: Miss Mary Matilda Maize

• Age: 26 years old• Profession: Professional

Sky Diver who knows that the best way to stay fit is to eat lot of vegetables.

Name: Tony Tuber

Suspected because:

Tony was caught at the local Safeway last year trying to sneak turnips out in his t-shirt.

Name: Randy Raddichio

Suspected because:

A witness saw Randy chowing down on some radishes just moments after the veggie snatching.

Name: Fanny Fennel

Suspected because:Fanny is also a skydiver and

the long time enemy of Miss Maize. She would like nothing more than for Miss Maize to not eat her vegetables and not be able to compete as well in the big competition next week.

• At each station there will be a question. If you answer the question correctly you will get a DNA clue.

• At the end, look at the clues and figure out who stole Miss Maize’s vegetables!

1. Presentation about DNA (Time: 15 minutes)2. Extracting DNA from an onion (Time: 15-20 minutes)

a. May be done as an experiment in front of the class rather than as an activity for everyone to participate in (as you need a blender, use of a knife, etc)

3. Making a DNA molecule with candy (Time: 15-20 minutes)

a) DNA molecule can be made with licorice as the backbone and mini marshmallows of different colours as the bases

b) Can the kids have food in class? (Any allergies?)

4. Playing a “CSI-style” mystery game (Time: 20-25 minutes)

a. The class will be broken up into groups of 2-4 children.b. I will present the case, with suspects and the victim of the crime (I

won’t choose a violent crime, something like a purse snatching!)c. There will be different stations where groups can get clues if they

answer questions right about DNA.