Punnett squares

What is a Punnett square?  That is what we had to figure out in our last two labs.  In my last post I talked about alleles and how they affect genetic traits.  Well it turns out that alleles are represented or written as capital and lowercase letters.  For example, if a trait determined whether a plant was tall or short, we could call that trait H for height.  If the allele was dominant we would write it as H, if it was recessive we would write it as h.  

The two alleles put together determine a trait's genotype.  For example: If the trait for a plant being tall was dominant it would be represented as H,  that means that the short gene is recessive or h.  That means that if a plant was short it's genotype would be hh, remember that both alleles have to be recessive for the organism to have the recessive trait.  If the plant was tall it's genotype would be either HH or Hh.

  Remember that if only one of the alleles is dominant the organism has the dominant trait.

So what does this have to do with punnett squares?  Well, a punnett square is a way that we can use two organism's genotypes to determine the chances their offspring will have certain traits.  The way this works is by creating a punnett square.  This is what a blank punnett square looks like.

it looks like... a square.  but it is really very helpful.  So, in our example let's say a tall plant "Hh" breed's with a short plant "hh".  We put those genotypes on the sides of the square like so.

After that we just cross the alleles and fill in the blanks.

From this we can determine that 50% of the offspring would be tall "Hh" and 50% would be short "hh".  This does not mean that exactly half of the offspring will be tall and the other half will be short.  This only shows that there is a 50% chance of the offspring being tall.  Just like if you were to flip a quarter twice you would not necessarily get one head and one tail, it's the same thing with this.  Hopefully I explained punnett squares well and did not bore you to death.

Earlobes

Yes, earlobes. In our recent lab we had to construct an earlobe pedigree showing whether members of our family have attached (B) or detached (A) earlobes. It is supposed to help us learn about how traits are passed from one generation to the next. Our pedigree is shown on the right.
During this lab we learned about how genetic traits are passed from one generation to another. Every trait is represented by two alleles, which are the sequences of DNA that show whether a person has that trait. One allele is contributed by each of your parents. Alleles can either be dominant or recessive. If both of the alleles are dominant or only one is dominant then that person has the dominant trait, in our example this would be unattached earlobes. However, both alleles would have to be recessive to have the recessive trait, in our example attached earlobes (like mine).

My Turn :)

Okay, it's my turn now! ;) 

Now that Noah has given us a great description of our experiments, I'll fill in everyone else on the process of Mitosis. 

As you can see in the diagram I put up, it shows the cycle of Mitosis beginning with the top circle and ending up back at the top with the same circle.

The purple circles are all cells, and if you can make out the white circles drawn inside them, that is the nucleus.  The green and red squiggles inside the white circle are the DNA strands.

Now, on with the show!

In the process of Mitosis, there are four stages.  If you've read this far and are wondering what Mitosis is, well, keep reading!  Basically, Mitosis is the a-sexual reproduction of eukaryotic cells.

The very first stage, which isn't listed in the four main stages of Mitosis, is the Interphase.  In this stage, the cell just does what it usually does and carries on an every day normal life, doing everything that it usually does.  This is illustrated in the very top circle.

The first official stage of Mitosis is the Prophase.  In this phase, the DNA (the green and red squiggles), and the centrioles (the small yellow cubes) all duplicate themselves.  The centrioles then begin to form the mitotic spindle which then attaches to the chromosomes (the red and green x-like structures that are now holding the DNA, illustrated in the 3rd circle).  Once the centrioles have completely attached themselves to the chromosomes, they begin to move outward.

Now we're getting to the second stage, the Metaphase.  In this phase, the centrioles begin to pull outward, making the mitotic spindle pull apart the chromosomes.  The cell then begins to stretch into a weird shape.

In the third stage, the Anaphase, the chromosomes split in the middle.  The chromosomes then begin to gravitate towards the centrioles.  This is illustrated in the 6th circle.  

In the fourth and final stage, the Telophase, the plasma membrane separates and the one cell pulls apart into two separate cells.  In each 'brand new' cell, there are chromosomes in each cell, and a centriole.  The chromosomes are then surrounded by a nuclear membrane forming the nuclei of the two cells.  This stage is illustrated in the 7th illustration.

So all summed up, a cells DNA copied itself, pushed the cells walls apart (with some help), split the cell apart, and created two new cells.  Reading this section in Biology really made me realize how amazing God is, and his creation...  :)

(This post was posted and written by Shasta A.K.A.  Gabe)

Mitosis

In this lab we just looked through the microscope at some cells that were reproducing. That week we had learned all about mitosis and how it works so we were a bit excited to see some actual cells. The first thing we looked at were some Ascaris cells; Ascaris is the largest type of parasitic roundworm in the world. Most of the cells that were undergoing mitosis were quite clear and we were mostly able to determine what stage of mitosis they were in. But when we looked at the allium onion root tip, it was very difficult to find cells that were in mitosis though we were able to find a few. The strangest thing we found was that in telophase the animal cells were blended together but the plant cells actually had a division between the two newly formed cells.

An interesting page about mitosis can be found here.

Deoxyribonucleic Acid

We began our experiment by putting split peas and water into a blender and churning them. Eventually we were left with what looked like a milkshake from your worst nightmare, a horrible green goo that looked bad and smelled worse.

After running it through a strainer which got out all the chunky parts, we put some clear hand soap into the thin green liquid that was left. The hand soap, when left for 10 minutes, dissolved the phospholipids and thus destroyed the plasma membrane, allowing the contents of the cell to flow out. After this we added a very small amount of meat tenderizer which contains enzymes that destroy proteins, this is what makes the meat more tender. In this case, The enzymes in the tenderizer destroyed the proteins surrounding the DNA, which allowed the DNA to leak out. We then added to the solution rubbing alcohol equal to the amount of liquid in the glass which floated on top of the solution.

In the end we were left with the bottom of the glass full of dissolved proteins which looked a lot like green mush. In the top of the glass, however, there were long strings of DNA which were difficult to see with, and impossible to see without a flashlight.

Pea DNA

Yesterday we had biology again.  We got to look at and study pea DNA.  It was interesting...  

If you look closely, you can see white stringy stuff in the glass.  That's the DNA from pea's.  I'll probably update this post later explaining how we did this...