Biology Junction Team - BIOLOGY JUNCTION

Who Ate the Cheese

Who Ate the Cheese?!

Introduction:

DNA isolation from blood, hair, skin cells, or other genetic evidence left at the scene of a crime can be compared with the DNA of a criminal suspect to determine guilt or innocence. This is due to the fact that every person has a different sequence. Scientists use a small number of sequences of DNA that are known to vary among individuals, and analyze those to get a possibility of a match. DNA is isolated, cut using restriction enzymes and sorted by size by gel electrophoresis. DNA is placed in a gel and an electrical charge is applied to the gel. The positive charge is at the top and the negative charge is at the bottom. Because DNA has a slightly negative charge, the pieces of DNA will be attracted to the bottom. The smaller pieces move more quickly towards the bottom than the larger pieces. The DNA can then be analyzed.

Objectives:

In this simulation you will examine crime scene evidence to determine who is responsible for eating the Queen’s special imported Lindbergher Cheese (yes, the stinky cheese). You will model the process of electrophoresis and DNA fingerprinting.

ROYAL GUARD INCIDENT REPORT

Incident Data

Incident Type:	Theft	Complaint Status	Pending DNA results
Processed by:	Chief Wiggam	Other Officers:	Officer Li Gase

Property

Property Code:	Rare cheese	Owner’s Name	Queen Elizabeth
Name:	Lindbergher	Value:	$12,000

Burglary Data

Method of Entry: Unknown, no evidence of force on doors or windows.

Narrative: The cheese was allegedly stolen from the Queen’s sitting room the night before the grand ball. The cheese was listed as a gift from the Manchurian diplomat. Officer Li Gase dusted for fingerprints and found none on the table or doors, the maid claimed that they had been wiped clean earlier. The wheel of cheese was on a platform in the sitting room, and half of it had been eaten. We took pictures of the half eaten cheese and sent it to the lab for further tests. Edna N. Zime, the lab technician said that saliva samples could be taken from the teeth imprints of the cheese that was left behind.

Suspect Data

Suspect Number: 1
Name: Princess Dubbah Elix
Description of Suspicion: The princess was seen entering the sitting room earlier in the evening. She is well known for her love of cheese.

Suspect Number 2
Name: Electra Foresis
Description of Suspicion: Electra was recently involved in a relationship with the Manchurian diplomat that sources say ended badly. Her motive may have been to sabotage the diplomat’s gift to the Queen.

Suspect Number 3
Name: Ada Nine
Description of Suspicion: Ada was the maid in charge of cleaning the sitting room. She had access to the cheese.

Suspect Number 4
Name: Gene Tics
Description of Suspicion: Gene is the leader of the local Cheese-Makers Guild, he may not have wished for Queen Elizabeth to have cheese from anywhere but his own guild.

Crime Lab Data

Crime Lab Investigator	R. Renee	Lab Technician	Edna N. Zime
List of Evidence Received	Plastic bag with cheese crumbs	List of Procedures Used	DNA extraction Polymerase Chain Reaction DNA restriction Analysis

Narrative: After receiving the package with the plastic bag marked Crime Scene, the DNA was extracted. Because the sample was so mall, the DNA was amplified using the polymerase chain reaction. We isolated the DNA from the four suspects and compared them to the crime scene DNA using DNA restriction analysis.

Results: See attached DNA Results

DNA Evidence Evaluation:

1. Turn your paper strips (DNA sequences) so that the side with the bases is facing you. The restriction enzyme cuts at every point it finds C C G G, always cutting between the C and the G. Label the back of the slips with the suspect number so that you don’t get them confused after cutting. Use scissors to cut the DNA sequence at the C C G G points.

2. Count the number of base pairs (bp) in each piece of DNA that you created. Record the base pair number on the back side of the DNA fragment.

3. Make an enlarged chart like the one shown. Your teacher will give you paper for this. Use a ruler to ensure that the lengths are uniform.

4. Tape your DNA fragments to the chart, using the base pair numbers as a guideline for fragment placement.

5. Compare the crime scene DNA to the suspects and indicate on your chart, which suspect is guilty of eating the cheese.

ANALYSIS:

1. On your chart, label the positive (+) and the negative (-) ends. Circle the suspect’s DNA who matches the DNA at the crime scene and write the name of the suspect.

2. For each of the following tasks performed in the activity, describe what they are actually simulating.

Cutting the DNA into fragments:

Taping the DNA onto the large paper:

3. For each word below, describe how it relates to DNA Fingerprinting:

Polymerase Chain Reaction:

Gel Electrophoresis:

Restriction Enzyme:

BACK

Where the Hippos Roam

Where the Hippos Roam
Holt, Rinehart, Winston

Introduction:

Millions of years ago, ancestors of modern crocodiles lurked in the shallow waters of lakes and other bodies of water. They hunted fish and other animals, much as their descendants do today. If you could travel back in time to visit one of those lakes, you might see the ancestors of today’s hippos there as well. Antelopes might browse along the edges of the lake, and rodents of various sizes might scurry back and forth. When paleontologists examine the fossil of a prehistoric organism, they may discover clues about the organism’s life. They may also answer questions about the environment it lived in: Was the area hot or cold? Was it humid or dry? Then, by putting all of these clues together, the paleontologists may be able to learn a little more about how organisms and environments change over time. Unfortunately, studying a fossil site is no easy task! Often, a paleontologist may find a few teeth scattered over a very large area. In such cases, keeping track of where the fossils were found is very important.

In this activity, you will use the data from a fossil site to create a map of fossil locations at that site. Then you will make some conclusions about the past environment, or paleoenvironment, at that location. The table below shows the locations of fossils that were found spread out over 22,500 m2. A team of paleontologists decided that this site, which measured 150 m x 150 m, was too large to work on all at once. Therefore, they decided to create a grid of 10 m squares.

Starting in the northwest corner, they labeled the squares with the letters A-O from west to east. Then the team numbered the squares 1-15 from north to south. In this way, each fossil could be labeled with a letter and a number, depending on where it was found. For instance, the label A1 would signify the 10 m x 10 m square in the northwest corner of the site. Similarly, the label O15 would indicate the square in the southeast corner of the site.

Activity:

Location of Fossils
Layer	Hippos	Rodents	Crocodiles	*Bovids
A	B11,C6,D3, I15,J10,L7, M6	C14,F7,G13, I3,L13,O2
B	F2,J3,K1,K2	B10,B11,F13	H2,I7,K2, N5,N7	G14
C	B3,C10,D1, H8,M9,N4	A5,A6,E2, E4,E14,H7, H8,H12,K4, M1,N15

* Bovids are antelopes and other similar animals

Problem:

Create a map of the fossil site. The scale should be 1 cm = 10 m. Label the grid of squares with letters and numbers.
Using letters, show where the fossils were found. (Put an H in each square where a hippo tooth was found; use R to indicate a rodent tooth, use C to show a crocodile tooth, and B for a bovid tooth.
Use a different color for each layer of sediment, and make a key to show which colors are which. (Example: Layer A – red, Layer B – blue, Layer C – green)
Based on the distribution of fossils in level B, what part of this site might have been covered by water? Devise a way to indicate that part on you map. (Example: Lightly shade with a color)

Questions:

Explain why you chose to shade part of your map as once covered in water. (What fossil clues helped you.)

Describe how the environment at this site changed through time.

One member of the team wished to look for fossils of dry-climate plants at this site. Which layer or layers do you think would be most likely to yield fossils of this kind? Explain your answer.

When the paleontologists were analyzing these data, they proposed several hypotheses to explain the changing climate. One of them suggested that tectonic uplift had occurred, causing the area to gain elevation over time. A second paleontologist disagreed, stating that the area probably lost elevation over time. Whom do you agree with? Explain your answer .

Water Properties Notes

Water Properties
States of Water
Adhesion and Cohesion
Surface Tension
Capillary Action

The States of Water

Water has three states. Below freezing water is a solid (ice or snowflakes), between freezing and boiling water is a liquid, and above its boiling point water is a gas. There are words scientists use to describe water changing from one state to another. Water changing from solid to liquid is said to be melting. When it changes from liquid to gas it is evaporating. Water changing from gas to liquid is called condensation (An example is the ‘dew’ that forms on the outside of a glass of cold soda). Frost formation is when water changes from gas directly to solid form. When water changes directly from solid to gas the process is called sublimation.


Gas	Liquid	Solid

Most liquids contract (get smaller) when they get colder. Water is different. Water contracts until it reaches 4 C then it expands until it is solid. Solid water is less dense that liquid water because of this. If water worked like other liquids, then there would be no such thing as an ice berg, the ice in your soft drink would sink to the bottom of the glass, and ponds would freeze from the bottom up!

Water is found on Earth in all three forms. This is because Earth is a very special planet with just the right range of temperatures and air pressures.

Adhesion and Cohesion

Water is attracted to other water. This is called cohesion. Water can also be attracted to other materials. This is called adhesion.

The oxygen end of water has a negative charge and the hydrogen end has a positive charge. The hydrogens of one water molecule are attracted to the oxygen from other water molecules. This attractive force is what gives water its cohesive and adhesive properties.

Surface Tension

Surface tension is the name we give to the cohesion of water molecules at the surface of a body of water. Try this at home: place a drop of water onto a piece of wax paper. Look closely at the drop. What shape is it? Why do you think it is this shape?

What is happening? Water is not attracted to wax paper (there is no adhesion between the drop and the wax paper). Each molecule in the water drop is attracted to the other water molecules in the drop. This causes the water to pull itself into a shape with the smallest amount of surface area, a bead (sphere). All the water molecules on the surface of the bead are ‘holding’ each other together or creating surface tension.

Surface tension allows water striders to ‘skate’ across the top of a pond. You can experiment with surface tension. Try floating a pin or a paperclip on the top if a glass of water. A metal pin or paper clip is heavier than water, but because of the surface tension the water is able to hold up the metal.

Surface tension is not the force that keeps boats floating.

Capillary Action

Surface tension is related to the cohesive properties of water. Capillary action however, is related to the adhesive properties of water. You can see capillary action ‘in action’ by placing a straw into a glass of water. The water ‘climbs’ up the straw. What is happening is that the water molecules are attracted to the straw molecules. When one water molecule moves closer to a the straw molecules the other water molecules (which are cohesively attracted to that water molecule) also move up into the straw. Capillary action is limited by gravity and the size of the straw. The thinner the straw or tube the higher up capillary action will pull the water (Can you make up an experiment to test this?).

Plants take advantage of capillary action to pull water from the into themselves. From the roots water is drawn through the plant by another force, transpiration.

Water Properties Prelab

Properties of Water

Pre-Lab Questions:

1. Explain why water is referred to as the universal solvent.

2. What is the overall charge on a molecule of water?

3. Water is a polar molecule (appears to have a charge). Explain why this is so.

4. Which end of a water molecule “acts negative”? Which “acts positive”?

5. Is water the only molecule that is polar?

6. Explain what occurs whenever several water molecules are near each other in a droplet. Include a sketch of this.

7. The property of water molecules being attracted to other water molecules is called ________________.

8. Explain what causes water to have surface tension.

9. Surface tension causes causes water to _____________ on surfaces such as glass.

10. In order to clean a surface, what must happen to surface tension? What type of chemicals can do this? Give an example

11. Besides reducing surface tension, what 4 other things can surfactants perform?

Water Properties Handout

Physical Properties of Water

All of water’s unique physical properties are caused by water’s polarity.

Cohesion: water molecules stick to each other. This is caused by hydrogen bonds that form between the slightly positive and negative ends of neighboring molecules. This is the reason why water is found in drops; perfect spheres. It’s hard to imagine water behaving any other way.

Adhesion: water molecules stick to other surfaces. This causes water to move upward against gravity in plant stems and to be absorbed by paper towels. It also causes water to adhere to spider webs.

Surface Tension: water has the ability to support small objects. The hydrogen bonds between neighboring molecules cause a “film” to develop at the surface.

Organisms like the water strider can be seen taking advantage of this property.

4. Water has a high boiling point. Water is one of the few substances that remain a liquid at such a large range of temperatures (O-100 °C). A large amount of energy must be invested to overcome the hydrogen bonds in liquid water to change it to the gas phase.

Liquid Water Molecules with hydrogen bonds Water Vapor Molecules

5. Capillary Action: water has the ability to “climb” structures. Think about what happens when you stick the tip of a straw in a glass of water.

6. Ability to Dissolve: water is consider to be the universal solvent. More substances will dissolve in water than any other liquid. This includes other polar substances (such as sugar) and ionic compounds (such as salt).

When a sugar crystal is placed in water, the slightly positive and negative ends of the water molecule attract the sugar molecules in the crystal (they are also polar) and pull them into solution.

When an salt crystals are placed in water, the slightly positive and negative ends of the water molecules attract the ions in the crystal. The ionic bonds holding the sodium and chlorine ions together are broken and the ions are pulled into solution.

7. High Heat of Vaporization: