Sarah A. Martinez January 27, 2010 Experiment #1

DNA INVESTIGATION

TEACHER’S INSTRUCTIONS

Note: This experiment is designed for 5th, 6th, 7th and 8th grade.

Activity duration 50 minutes

Objectives

This experiment will notonly teach students how to carry out molecular techniques such as isolating DNA from salmon nuclei, but it will also teach them what DNA is, and how to use a microscope.

Background story

The students are research scientist investigators working for the police department and in order to be able to earn the qualifications to isolate DNA from human samples the head researcher of the lab gives them a tube with salmon nuclei on it and expects them to isolate DNA from it.

In this experiment the students will isolate DNA from salmon nuclei.

DNA also known as Deoxyribonucleic acid is a genetic material that is in all living cells. DNA is shaped like a double helix, made up of two anti-parallel chains, made up of four bases: adenine, guanine, cytosine and thymine. Each person has his or her own DNA that no one else in the world has.

In this experiment we are going to show the students animal slides under a microscope, and teach them how to use a microscope. Then as the instructor, you should take a few drops of the salmon nuclei and put it on a slide with a cover slip and look at the nuclei. Then each student will get to play with spooling DNA. Nuclei are not soluble in water due to the lipid envelope. The addition of SDS will dissolve the envelope releasing the DNA, which then makes them uncoil and then become clear in solution. Since DNA does not dissolve in alcohol, the addition of alcohol makes the DNA becomes visible again.

Materials

  • 1-mL transfer pipettes (3 per student)
  • Glass rods (1 per student)
  • 13mm glass tube (1 per student)
  • 95% ethanol (3 to 4-mL per student)
  • 10% SDS (4-5 drops per student)
  • Sperm nuclei from salmon (0.5g in 100mL water) can be purchased from Carolina Biological Lab
  • Microscope slides
  • Microscope cover slips
  • Microscopes
  • Example animal slides

Instructions

  1. Add 2-mL of the Salmon nuclei into a 13mm tube
  2. Add 5 drops of 10% SDS into the 13mm tube, flick the tube and watch the nuclei disappear (the solution will turn clear)
  3. Tilt the 13-mm tube to a 45º angle and add 3-4-mL of Ethanol
  4. With your glass rod spin the mixture in one direction and pull the DNA along the side of the tube

Outside preparation

The salmon nuclei needs to be prepared an hour before the experiment is conducted the formula is (0.5grams of the sperm nuclei in 100 mL of water)

Experiment Variations

This could be done with bacterial DNA such as Halobacterium volcanii. It could be presented to the students as another task they have to complete in order to get a promotion in their lab. The steps include:

  1. Add 5-mL of tap water to the lawn of Halobacterium petri dish. Make sure all of the water is distributed over the whole plate. Be sure to wait three minutes before moving to the next step. This step will break apart (lyse) the cells
  2. Pour the liquid (lysate) gently into the test tube
  3. Put 3- 4 mL of cold ethyl alcohol. To ensure that the lysate and the alcohol layer do not mix tilt your tube to a 45 degree angle and gently drop the alcohol on top of the lysate
  4. Let the tube sit for 20 minutes. This step allows the DNA to come out of the solution. After 20 minutes the solution should look stringy
  5. With your glass rod, tilt your tube to a 45 degree angle and spin your rod in one direction, mixing the two layers (BE VERY GENTLE MIXING BECAUSE IF YOU ARE TOO ROUGH YOU WILL BREAK THE DNA)
  6. After mixing you will see material on your glass rod and that is DNA

References

DasSarma, Priya, and Shiladitya DasSarma. "Extremely Easy DNA Extraction Kit." Carolina 15.4773 (2006): 1-6.

Experiment #1

STUDENT WORKSHEET

Background story

Each person has his or her own unique DNA; it makes us who we are. DNA is what makes people in the same family look alike.

Below is a picture of a cell, inside a cell there are chromosomes, and chromosomes are made of very tightly coiled DNA, our goal today is to isolate DNA.

Today we are going to look at various animal cells under a microscope.

In below box, draw a picture of the slide you find most interesting.

Draw below what the salmon nuclei looks like under the microscope

You are all research scientist investigators working for the police department and in order to be able to earn the qualifications to isolate DNA from human samples the head researcher of your lab gives you a tube with salmon nuclei on it and expects you to isolate DNA from it.

Instructions

  1. Add 2-mL of the Salmon nuclei into a 13mm tube
  2. Add 5 drops of 10% SDS into the 13mm tube, flick the tube and watch the nuclei disappear (the solution will turn clear)
  3. Tilt the 13-mm tube to a 45º angle and add 3-4-mL of Ethanol
  4. With your glass rod spin the mixture in one direction and pull the DNA along the side of the tube

Congratulations you have isolated DNA fromsalmon nuclei!!!!

Write a few words describing what you learned about DNA today

Color in the DNA following the instructions

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