Background Information” DNA and gel electrophoresis.

A. The structure of DNA

1. DNA, or deoxyribonucleic acid, is a very large molecule called a polymer. Polymer means molecule with many units. The units or monomers of DNA are called nucleotides.

a. Nucleotides are made up of a 5-carbon sugar (deoxyribose) a phosphate group and one of four nitrogen bases. The bases use letters to shorten their names.

1. A is for adenine

2. G is for guanine

3. C is for cytosine

4. T is for thymine

b. Purine Bases -- Adenine and guanine are purines. Purines are the larger of the two types of bases found in DNA. They have a double ring structure.

c. Pyrimidine Bases -- Cytosine and thymine are pyrimidines. They have a single ring structure.

2. Deoxyribose Sugar -- The deoxyribose sugar of the DNA backbone has 3 oxygen and 5 carbon atoms. The hydroxyl groups carbons link to the phosphate groups to form a DNA backbone.

3. DNA is composed of twisting strands of nucleotides. Each strand is a Helix or spiral staircase. The two strands bound together make DNA a double helix.

4. In the structural configuration of DNA, A and T always join together and form two hydrogen bonds while C and G always join together and form three hydrogen bonds. Because of the specificity of base pairing, the two strands of DNA are said to be complementary. This characteristic makes DNA unique and capable of transmitting genetic information.

B. DNA Fingerprinting


1. DNA Fingerprinting is a method of identification that compares fragments of DNA. DNA is the genetic material found within the cell nucleus. An individual's DNA is as distinctive as a fingerprint. With the exception of identical twins, the complete DNA of each individual is unique.

Student work in Paint

2. A DNA fingerprint is constructed by first obtaining a DNA sample from body tissue or fluid. The sample is then cut into pieces using enzymes and the segments are arranged by size using a process called gel electrophoresis.

3. Gel electrophoresis is a method that separates macromolecules like DNA on the basis of size, electric charge, and other physical properties.

a. A gel is similar to Jell-O in consistency. The term electrophoresis describes the migration of charged DNA particles under the influence of an electric field. Electro refers to the energy of electricity. Phoresis, from the Greek verb phoros, means "to carry across." Thus, gel electrophoresis refers to the technique in which molecules are forced across a span of gel motivated by an electrical current.


b. Holes are created in the gel that serves as a reservoir to hold the DNA solution.

c. DNA solutions (mixtures of different sizes of DNA fragments) are loaded into a well in the gel.

d. The gel matrix acts as a sieve for DNA molecules. Large molecules have difficulty getting through the holes in the matrix. Small molecules move easily through the holes because of this, large fragments will lag behind small fragments as DNA migrates through the gel.

e. Results are usually photographed in order to save the findings. Wells are then compared together for similarities. If two fingerprints match they are probably from the same DNA source (i.e. Crime scene blood and suspect blood.)

4. DNA fingerprinting technology has helped scientists to discover the genetic causes of many disease processes. Mapping the entire Human Genome (all of our DNA) has been one of the most massive scientific endeavors of all time. The complete human genome was completed in 2003.

1.  DNA fingerprinting helped advance forensic science and paternity testing. Which 2 DNA samples match?

Project:

Create a visualization of DNA and gel electrophoresis

Introduction: Students will create a multimedia presentation of DNA and gel electrophoresis.

Materials:

·  3D animation software such as 3D StudioMax or trueSpace

·  Research medium such as the Internet

Requirements:

1. Students are to work independently.

2. Using 3D animation software, students need to animate the process of gel electrophoresis.

3. Students should research the topic and develop a storyboard for their presentation.

4. The student should have the following modeled in their animation:

·  Gel box

·  power supply

·  power electrodes

·  identification of the negative and positive

·  sides of the gel box

·  identification of the sources of the DNA

·  (i.e. suspect, mother, father, evidence)

5. The student needs to have the following animated in their project:

·  the DNA being deposited into the gel box at the proper location

·  movement of the DNA fragments through the gel

·  A close up from a camera placed in the scene of the results

·  Proper lighting instead of default lighting (see unit on lighting)

·  Text that appears after the DNA has stopped moving, explaining the results

Variations: Advanced students can add PCR to their presentation. Place in Premiere with music and voice over.

Assessment:

All models are drawn correctly 30 points

Animation works correctly 30 points

Text is used to label the animation 15 points

Results are shown and explained 10 points

Correct color, size, lights and view of animation 15 points

Total 100 points

Rubric:

All models are drawn correctly

3 or more of the following are not correct.
The Gel box, gel, power supply, power electrodes, negative and positive ends, and sources of the DNA are drawn correctly and to scale. / 1-2 of the following are not correct.
The Gel box, gel, power supply, power electrodes, negative and positive ends, and sources of the DNA are drawn correctly and to scale. / The Gel box, gel, power supply, power electrodes, negative and positive ends, and sources of the DNA are drawn correctly and to scale.
/ Total
Points
0-19 points / 20-29 points / 30 points

Animation works correctly

2 or more of the following do not work correctly.
The DNA is loaded in the gel, the DNA moves down the gel towards the positive end, and the results are animated correctly. / 1 of the following does not work correctly.
The DNA is loaded in the gel, the DNA moves down the gel towards the positive end, and the results are animated correctly. / The DNA is loaded in the gel, the DNA moves down the gel towards the positive end, and the results are animated correctly. / Total
Points
0-19 points / 20-29 points / 30 points

Text is used to label the animation

3 or more of the following labels are missing and not visible at the correct time.
3D text is used to label each well with the source of the DNA. 3D text is used to label the results. Text becomes visible at the correct time. / 1-2 of the following labels are missing and not visible at the correct time.
3D text is used to label each well with the source of the DNA. 3D text is used to label the results. Text becomes visible at the correct time. / 3D text is used to label each well with the source of the DNA. 3D text is used to label the results. Text becomes visible at the correct time. / Total
Points
0-9 points / 10-14 points / 15 points

Results are shown and explained

The gel does not show a match between two of the DNA samples and the matching wells are not labeled to explain the results (i.e. blood at crime scene matches the victim’s DNA.) / The gel does not show a match between two of the DNA samples or the matching wells are not labeled to explain the results (i.e. blood at crime scene matches the victim’s DNA.) / The gel shows a match between two of the DNA samples. The matching wells are somehow labeled to explain the results (i.e. blood at crime scene matches the victim’s DNA.) / Total
Points
6 0-00g 0-5 points / 6-9 points / 10 points

Correct color, size, and view of animation

2 or more of the following are incorrect.
The animation uses correct color (see unit on color.) The models fill most of the scene. The camera is used correctly to zoom in on the results. Lights are placed properly to correctly light the scene. / 1 of the following is incorrect.
The animation uses correct color (see unit on color.) The models fill most of the scene. The camera is used correctly to zoom in on the results. Lights are placed properly to correctly light the scene. / The animation uses correct color (see unit on color.) The models fill most of the scene. The camera is used correctly to zoom in on the results. Lights are placed properly to correctly light the scene. / Total
Points
0-9 points / 10-14 points / 15 points


DNA and Gel

Electro – phoresis