Strawberry DNA Extraction

Put strawberries and a plastic bag. We used about three good-sized ones.

Add a teaspoon or so of water and mushed up the strawberries.

Carefully pour only the liquid of the strawberries into a test tube. Try to avoid clumps of strawberries. I have my test tubes packed, so I used a clean spice jar.

Add 1/4 teaspoon of dish washing soap. Stir it up with a wooden skewer or just shake the tube around a little to mix together.

Very carefully add ice cold rubbing alcohol (from the refrigerator) to the test tube. You want the alcohol to remain on top of the strawberry juice.

Now just watch and see something amazing happen in just minutes.

We have DNA! The little white strands are what you are looking for.

The Science Behind It

In higher organisms like plants and animals, DNA is stored in a compartment called a nucleus where the long, string-like DNA is tightly coiled. To separate DNA from the organism that contains it, you have to break the cells apart (lysis), filter out the big pieces of cell parts and collect the remaining liquid, or supernatent, and add chemicals like salt and alcohol to separate (precipitate) the DNA from the rest of the supernatent.

Sources: {Our} Life's Adventures

You Tube
The Kitchen Pantry Scientist

Easter Egg and M & M's Genetics

Remember when we learned how to complete Punnett Squares?

If  you were looking for a more visual, hands-on way to practice their Punnett square-solving-skills, you can use plastic eggs leftover from Easter.

Assign a genotype to each egg color, such as the following:

Blue - BB

Green - Bb

Yellow - bb

This example uses incomplete dominance - i.e. Bb appears green, not blue, as it would in a straight dominant/recessive situation.

The eggs have been mixed and matched to create various genetic crosses. For example, a blue half matched with a green half would represent BB x Bb.

Now have your students use a Punnet square to solve the cross, and then open the egg to check their work!

 Access Excellence Activities-To-Go Collection

has a worksheet your student can use to determine the Punnett Squares and the results.

Source: Science Matters

The Environmental Factor in Genetics and Its Effect on Radish Leaf Color

"...an organism's characteristics are not wholly determined by genetics. There are environmental factors...that influence the makeup of an organism. With all the talk of Punnett squares and the emphasis on phenotypes that are completely determined by genetics, it is important to remind ourselves that genetics is not the only thing at play. We can observe the effect that the environment has on a genotype to make its phenotype change." -Jay Wile, Exploring Creation with Biology

We planted 60 radish seeds in two egg cartons, wetting the soil. We covered one egg carton with a box to keep out light and let one have sunlight. When half of the seeds sprouted, we examined them daily. The cotyledons (the two leaves in the sprout) were either yellow or green.

We discovered that those seeds in the light had some yellow cotyledons to begin with but turned green over time. Those left in the dark continued to stay yellow, and in fact, even the ones that were green to start with, turned yellow over time. By the end of a week of observation, all of the cotyledons in the egg carton in the dark were yellow and all of the cotyledons in the egg carton in the light were green.

Genetic traits can be influenced by environmental conditions.

Genetics, Part 4: Punnett Squares

Sam has been having fun with Punnett Squares. We read about Gregor Mendel's experiments with pea plants and about dominant and recessive genes. We then began making Punnett Squares. A Punnett square is a diagram that is used to predict the outcome of particular genetic traits. You would, for example write the genetic traits of the mother on one side of a square and the paternal traits on top of the square and the square is then divided into four smaller sections and we look at the combinations possible.

After looking at a few Punnett Squares having to do with Mendel's pea plants, I gave Sam a problem (from My Name is Gene) about a couple, Bill and Jane. Bill's great grandmother had died from sickle cell anemia. Their first child also came down with the disease. What would the Punnett Square for Bill and Jane look like and what is the chance of their next child developing the disease?

All characteristics are noted by the dominate trait with a capital letter and the recessive trait with a lowercase letter. We shall say that they gene for sickle cell anemia is s.

Above is the Punnett Square Sam made. Because both Bill and Jane do not have the disease themselves, but one needs ss in order to have the disease, we can only assume that both Bill and Jane have Ss gene traits, or genotype.

Sam wrote these along the top and side of the square. (Yeah, I know it is hard to tell upper and lowercase with his handwriting, but you are just going to have to trust me on this one.) Then, making the square inside as a four-squared chart, he then put together the combinations by putting together the letters from the side and top of each individual small square, coming up with SS,Ss,Ss and ss.

From the Punnett Square ss genotype is in one quadrant out of four, which is 25%. Each time they have a child the probability of the child with the disease will always be 25%.

A hands-on way of learning Punnett Squares can be found here.

Genetics: Week 3: Mitosis Model

Jello Cell Model
The DNA hangs out in the Nucleus (the marshmallow in this picture.)
Let's go further in.

Cell division is a biological process by which a cell divides into two or more cells. During this division the nucleus splits and the DNA is replicated. One of the two types of cell division is called mitosis. In mitosis the parent cell divides into daughter cells, each with a complete copy of the genetic material of the parents, and with the capacity to divide again.

page from My Name is Gene

When I saw this simple and easy mitosis model at Journey into Unschooling, I wished I had thought of it when Katie had biology. It is so simple and yet it helps to understand and remember the stages of mitosis.

It's mitosis -- with yarn, plates and pipe cleaners!

Here we have a strand of DNA inside a plate cell.

Now, let's get in closer to the DNA and exchange the yarn for pipe-cleaners. With just a snip and a twist, we can see...

Interphase

This is the normal state of a cell. It's just going about its daily business of surviving and making sure it has all of the nutrients and energy it needs. It is also getting ready for another division that will happen one day. It is duplicating its nucleic acids, so when it's time for prophase again, all the pieces are there.

Prophase
A cell gets the idea that it is time to divide. First, it has to get everything ready -duplicate DNA, get certain pieces in the right position, and generally prepare the cell for the process of mitotic division.

  Metaphase
Now all of the pieces are aligning themselves for the big split. The DNA lines up along a central axis, an invisible line.

Anaphase

The separation begins. Half of the chromosomes are pulled to one side of the cell; half go the other way.

Telophase

Now the division is finishing up. The cell into two pieces. You have two separate cells each with half of the original DNA.

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Genetics, Part Two-B: Plant Cell Model

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For the plant cell, I used Katrina's idea at Baking and Boys! and used a cookie pizza. We spread out the dough on a baking sheet to make it rectangular, just like plant cells. Sam then used candy to represent the various cell components. You could use whatever you have on hand.

Plant Cell

Cell Wall-pizza pan

Cell Membrane-chocolate frosting

mitochondrion - hard orange candy

Nucleus- Marshmallow

Nucleolus- Gumball

Ribosomes-M & M's

rough endoplasmic reticulum - (rough ER) -Gummy worms

smooth endoplasmic reticulum - (smooth ER) -Candy Sticks
Cytoplasm: Cookie Dough
Amyloplast: gum drop
Chloraplasts: Green "chews" (like taffy)
Centrasome- Peppermint

Next week we will be making models of Mitosis with three colors of pipecleaners.

Genetics, Part Two-A: Animal Cell Model

This week we learned about cells.

We made a model of an animal cell, using Jello. (Directions for an example of this can be found at Enchanted Learning.) They estimate the appropriate grade level as 5-7th, but I did it with some older and some younger than this.

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Light colored Jello works the best for this but I forgot we were going to do this week and had to use what we happened to have in the cabinet, which was orange.  I decided to make the animal cell in a pie pan so that it would be circular. You will also need various candies used to represent the parts of the cell. I just got out our bowl of candy and used what we had on hand. Our choices are different from the ones at Enchanted Learning.

First, make the Jello but with a bit less water than the instructions call for. This will make the gelatin a little stiffer and will make the cell components stay in place better. Put the Jello in the refrigerator  for about an hour to set a little.The gelatin will represent the cytoplasm of the cell. Then we began adding the cell components and we went over each candy item and what part of the cell it represented as we built our model and then sketched it.

cell membrane - the thin layer of protein and fat that surrounds the cell. (pie pan)

centrosome - a small body located near the nucleus - it has a dense center and radiating tubules. This is where microtubules are made. During cell division (mitosis), the centrosome divides and the two parts move to opposite sides of the dividing cell. (peppermint)

cytoplasm - the jellylike material outside the cell nucleus in which the organelles are located. (jello)
Golgi body - (also called the Golgi apparatus or Golgi complex) a flattened, layered, sac-like organelle that looks like a stack of pancakes and is located near the nucleus. It produces the membranes that surround the lysosomes. The Golgi body packages proteins and carbohydrates into membrane-bound vesicles for "export" from the cell. (Mike and Ikes)

lysosome - (also called cell vesicles) round organelles surrounded by a membrane and containing digestive enzymes. This is where the digestion of cell nutrients takes place. (spice drops)

mitochondrion - spherical to rod-shaped organelles with a double membrane. The inner membrane is infolded many times, forming a series of projections (called cristae). The mitochondrion converts the energy stored in glucose into ATP (adenosine triphosphate) for the cell. (Gummy worms)

nucleus - spherical body containing many organelles, including the nucleolus. The nucleus controls many of the functions of the cell (by controlling protein synthesis) and contains DNA (in chromosomes). and

nuclear membrane - the membrane that surrounds the nucleus. (marshmallow)

nucleolus - an organelle within the nucleus - it is where ribosomal RNA is produced. Some cells have more than one nucleolus. (gumball)

ribosome - small organelles composed of RNA-rich cytoplasmic granules that are sites of protein synthesis.
rough endoplasmic reticulum - (rough ER) a vast system of interconnected, membranous, infolded and convoluted sacks that are located in the cell's cytoplasm (the ER is continuous with the outer nuclear membrane). Rough ER is covered with ribosomes that give it a rough appearance. Rough ER transports materials through the cell and produces proteins in sacks called cisternae (which are sent to the Golgi body, or inserted into the cell membrane). (M & M's)

smooth endoplasmic reticulum - (smooth ER) a vast system of interconnected, membranous, infolded and convoluted tubes that are located in the cell's cytoplasm (the ER is continuous with the outer nuclear membrane). The space within the ER is called the ER lumen. Smooth ER transports materials through the cell. It contains enzymes and produces and digests lipids (fats) and membrane proteins; smooth ER buds off from rough ER, moving the newly-made proteins and lipids to the Golgi body, lysosomes, and membranes.
vacuole - fluid-filled, membrane-surrounded cavities inside a cell. The vacuole fills with food being digested and waste material that is on its way out of the cell. (Twizzlers)

Once you are finished, put in the refrigerator to fully set. Then you can eat it, if you wish.

Another excellent idea is to make the model from a pizza! Journey to Excellence shows this example.

 

Next week we will be making models of Mitosis with three colors of pipecleaners.

Genetics, Part I: DNA

Sam making DNA model, 3/30/09

For the next few weeks we are going to be studying genetics using the book My Name is Gene, which is written for grades 5-8, but I will also be doing some additional hands-on activities that even my younger boys can do. The first chapter includes information about Crick and Watson who discovered the molecular structure of DNA and also about the double helix structure and the nucleotides. For the activity for this chapter, I wanted the boys to make models of DNA, including the appropriate pairing of the nucleotides.  

Sam did this activity a few years ago, (and years ago at a co-op class with Katie) but I was pretty sure he would do it again, and help his little brothers with it.

What You Will Need:

Four pipe cleaners, any color

50 pony beads (or you can use pieces of colored straws): 17 in one color (color 1), 17 in another color (color 2), four in four other colors (colors 3, 4, 5 and 6) 

Cut two pipe cleaners into 6-inch lengths. Alternate stringing color 1 and color 2 beads on each pipe cleaner until you have 17 beads on each. Fold back the excess length of pipe cleaner to hold the beads in place. These will be the strands of your DNA.

Cut the remaining pieces of pipe cleaner into eight 2 1/2-inch strips. String four pieces with pairs of color 3 and color 4. String the remaining four pieces of pipe cleaner with pairs of color 5 and 6. These will form your base pairs. These represent the four nucleotides adenine, cytosine, guanine and thymine. Adenine always pairs with thymine and cytosine always pairs with guanine. Have your students pick what colors represent the different nucleotides and then make a color key.

Twist your base pair pieces around the strands of your DNA to attach so that there are two strand beads between each set of base pairs. Position each base pair horizontally and evenly around your strands. Make sure to attach these identically on both sides so that your color 1 and color 2 beads match up. Hot glue your pieces in place if desired.

Twist your strands to form your DNA into a double helix. Now you have a model of a DNA sequence.

We attached two together to make this long strand.

And, if this is too complicated for you, Journey Into Unschooling has an even simplier way of doing it with Post-It Notes. And this one will lay flat in a notebook!

Next week we will be studying plant and animal cells and making models of those.
You will need a package of light colored Jello, some chocolate chip cookie dough and various candies for that one.



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