DNA Instruction Molecule 9-14 yrs

Cells are tiny, round essential entities (like bricks), assembled together to make your own body. Your body is built of trillions of cells (10,000,000,000,000) and each cell has its own job. Plants and other animals are made of different types of cells.

The genetic information for making every cell of your body is contained in the chromosomes. In animals and plant cells, chromosomes are segregated in the nucleus of the cells. The chromosomes are what is transmitted from one mother cell to a daughter cell when a new cell is built. Chromosomes are also the information transmitted from the parents to the baby.

The human genome is composed of 23 pairs of chromosomes per cells, while Chimpanzees have 24 pairs, Cows 30 pairs, Chickens 39 pairs, Fruit flies 4 pairs, and Bananas 11 pairs. It is made of pairs because one copy comes from the mom and the other copy from the dad. Our genome is 98.5% identical to the DNA of Chimpanzees.

Chromosomes are the condensed structure of the DNA molecule (Deoxyribo Nucleic Acid). DNA is the biological instructions/molecule that contains the genes, which encode for every cell’s and organism’s components, structure and purpose. In other words, DNA is a record of instructions telling the cell what its job is going to be. The genes are written in a molecular alphabet of 4 “letters/molecules”: A, T, C, and G. A stands for Adenine [ˈædÉ™nɪn], T for Thymine [ˈθaɪmiːn], C for Cytosine [ˈsaɪtÉ™sɪn] and G for Guanine [ˈɡwɑːniːn]. While A and T only pair together, C and G only pair together. Organized sequences of these A-T, T-A, G-C and C-G pairs form the genes. In 2003 the human genome (the complete set of genes to make a human being) has been completely sequenced and most of the genes mapped. So far, your genome is known to contain close to 20,000 genes each of them coding for a specific function.

The genetic information is what makes you physically similar to the other people around you, but also makes you different. Natural genetic variation (the order of the A-T and C-G pairs) is what makes hair, skin or eyes color, height, male or female different. Each person has their own version of the “human instruction manual” and only identical twins share the exact same genetic information. When a mistake happens in the ATCG text it is called a mutation and it can cause genetic diseases such as albinism or dwarfism.

A DNA molecule has a coiled braid or ladder shape that has been twisted into a corkscrew: two strands are tight together like jigsaw puzzle pieces and that’s called the double helix. One strand of the molecule is the "negative" of the other and both strands serve different instruction purposes. The strands are made of Deoxyribose (sugar) and phosphoric acid, with the corresponding 4 organic bases A, T, C and G inside the strands.

Picture DNA as a ball of wool. All your DNA is densely packed into 23 pairs of chromosomes that form the human genome. Now if you were to unravel the DNA strand, imagine rolling the ball of yarn along the floor, the DNA strand would measure 2 meters (6 feet long) ­– just for one cell. If you took the DNA strands in every cell of your body and stretched them out, you could make a DNA line all the way to the Moon.

Different species have different DNA sequences, and different numbers of chromosomes, depending on the quantity and organization of their genes and DNA molecules.

In 1953, James D. Watson & Francis Crick got the Nobel Prize of Medicine for their discoveries concerning the molecular structure of nucleic acids (DNA) and its significance for information transfer in living material. Their model of the DNA double helix is mostly based on an X-ray observation from another scientist Rosalind Franklin before she had the chance of formally publishing her data. No acknowledgement was publicly given to Rosalind at that time.

Here is a video you can all watch about DNA, the instructions contained in genes and different species genomes: http://kidsciencestuff.blogspot.ca/2009/12/dna-video-for-kids.html

DNA Extraction

Time: Approximately 45 minutes

INSTRUCTIONS:

1. Peel the kiwi and chop it into small chunks (remove the brown skin. It is dead and doesn’t have much DNA).
2. Put the chunks in a plate and mash the kiwi as much as you can; this helps break the cells apart. Put the mashed kiwi into a Ziplock bag.
3. Mix together the dish soap, salt, and water very slowly until the salt is fully dissolved. Try not to make bubbles! This mixture is your extraction buffer. The soap breaks up the cells, while the salt helps the DNA dissolve in water.
4. Add the extraction buffer to the mashed up kiwi and close the bag, leaving no air inside. Slowly and thoroughly mix by gently pressing back and forth on the bag.
5. Let the mixture stand (incubate) for 20 minutes at room temperature.
6. Filter the kiwi and buffer mixture through the coffee filter into a clean, transparent glass. You should be left with a green liquid that contains the kiwi DNA.
7. Gently pour the cold alcohol gently on the inside wall of the glass. The alcohol will form a transparent layer on top of the kiwi mixture. Because the DNA cannot dissolve in alcohol, at the interface between the kiwi mixture and the alcohol you will see a white jelly-like precipitate. Do not mix; this is the DNA. You can hook the DNA out using a fork or a stick.

The DNA you’ve extracted comes from billions of kiwi cells, which is why you can see it. However, DNA is so thin (2 nanometers in diameter, which is 10,000 times smaller than a human hair) that if you unravel it you won’t be able to see a single DNA strand without an incredibly powerful microscope.

Build a DNA Molecule with Origami

Time: 25 minutes including a quick colouring.

If you unravel the DNA molecule that you’ve just extracted from the kiwi and observe it under an X-ray microscope, this is what it would look like.

INSTRUCTIONS:

1. Pick 4 colors and fill in the blanks always pairing the same two together. Make sure A is only paired with T and C only paired with G. Write the corresponding bases in boxes diagonally across from your sequence.
2. Fold in half lengthwise. Make all creases as firm as possible (use your fingernails).
3. Hold the paper so that the thick lines are diagonal and the thin lines are horizontal. Fold the top segment down and then unfold.

For more detailed instructions go to http://www.yourgenome.org/activities/origami-dna and select if you want the Instructions for Coloured Template or Instructions for Blank Template.

Build a DNA Molecule Using Candies

Time: 15-20 minutes

This is the DNA molecule that is condesned in the jelly blob that you just extracted from the kiwi.

INSTRUCTIONS:

1. Take out four red, four clear, four yellow and four green Gummy Bears.
2. Carefully thread a green and clear Gummy Bear onto a toothpick (be careful not to poke your fingers while doing it). The Gummy Bears should touch each other and meet in the middle of the toothpick leaving extra space on either side of the toothpick.
3. Reproduce step #2 pairing the 3 other green and clear Gummy Bears.
4. Thread the red with the yellow Gummy Bears the same way that you did with the green and clear. You should have 8 pairs of Gummy Bears onto toothpicks.
5. Randomly put each toothpick in the middle of the two strands of Twizzlers.
6. Twist it a little and you have your double DNA strand. Your body contains one billion times more of what you have here (in terms of number of pairs).