Friday, Dec. 12, 2008

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For the Catalyst today in Period 8 we attempted to decode secret messages written in DNA nucleotide bases by our counterparts in Period 4. There was some confusion and so I partially solved the first of the 3 secret messages for the class on the whiteboard. To review once again:

The DNA molecule is like a step-ladder, where the center rungs are molecules called nucleotides. There are 4 kinds of nucleotides that we abbreviate with A, T, G, and C.

A and T always go together.
C and G always go together.

Wherever there is an T on one side of the DNA, it will pair up with a A on the other side (and vice-versa). Wherever there is a G on one side of the DNA, it will pair up with a C on the other side (and vice-versa).

I guess Aaron put it simplest when he said, "Replace all the A's with T's and T's with A's and then replace all C's with G's and G's with C's."

That's the root of it, and the fact that these particular nucleotide bases always pair together is known as Chargaff's Rule.

So, Step 1 towards solving the puzzle was to transcribe, or translate (or as Aaron put it, "replace") all of the nucleotide bases in the DNA code with their complementary pairs, or partners (A with T and C with G). This is similar to how certain enzymes in the cell (like DNA polymerase) "unzip" the DNA strand and "read" a gene while constructing a messenger RNA molecule, a.k.a., mRNA (similar to half a DNA strand). The mRNA is then "read" by a ribosome and turned into a protein. It's like opening the DNA blueprint and making a copy so that you can safely bring the plans with you to the construction site without risking the originals.

Step 2 involved breaking the long mRNA string down into codons, or sets of 3 letters each that will "code" for a particular amino acid (or letters, in our case), that will in turn be used to construct proteins (or for us, words).

For example, the first few letters in the first half-DNA strand were... CAGGTAGCACCT.

First, I'm going to use Chagraff's Rule to change all the T's to A's and G's to C's.

C A G G T A G C A C C T -->
G T C C A T C G T G G A

Then, I break it into 3-lettered codons: CAG GTA GCA CCT

Then, I look up these letters in the Key, which represents the ribosome "factory" that will use the DNA blueprints to "build" amino-acid letters, step-by-step and codon-by-codon at a time. According to our Key found in Catalyst problem number 1, the above 4 codons would results in the amino acids "T," "A," "C," and "O." So our first protein-word is "Taco."

Someone in 4th period has a secret message for you about Taco's! Intrigued? I sure was.

Everyone was required to complete this Catalyst Exercise as their Exit Ticket out the door before class was over. Also due today was the homework from last time which consisted of 8th Period's own secret messages for the students in 4th Period.

Homework for this weekend is: Write 5 Sample Exam Questions, just like you'd see on the Midterm. Make them Multiple-Choice, and be sure to include the possible answers, A-D. Use your Study Guide and Textbook for help and direction. We will be quizzing each other on Monday.

> Download the Daily Catalyst.

> Download the Unit I and Unit II Study Guide.

> Download the Study Guide Answer Key.

What's the Deal with DNA?

DEOXYRIBONUCLEIC ACID!

That's what DNA stands for. It's a super important molecule inside the nucleus of every single cell in your body. It...

• Controls all the activities of the cell



• Contains the information to make new cells



• Provides instructions for making proteins

In other words, it is nothing less than the Blueprints for Life! Ever wondered why your eyes, hair, and skin are the color they are and not something else? Or why some people have dimples, are double-jointed, can roll their tongue into funny shapes, and other can't? It's all because of DNA.

DNA is a long string of molecules bonded together. The first scientists to discover the odd shape of DNA were James Watson and Francis Crick, with the help of x-ray photographs taken by Rosalind Franklin (nice last name, huh?). Together they determined that DNA is shaped like a twisted ladder called a double helix.

The sides of the double helix are made of sugar and phosphate molecules. The center rungs that stretch in between are called nucleotides, and there are 4 types.

Adenine (A) Thymine (T)
Cytosine (C) Guanine (G)

In the 1950's, a scientist named Erwin Chargaff discovered that the amount of Adenine (A) in DNA always equaled the amount of Thymine (T), and the amount of Cytosine (C) always equaled the amount of Guanine (G). That's because Adenine (A) always pairs with Thymine (T), and Cytosine (C) always pairs with Guanine (G). This is known as Chagraff's Rule.

Chagraff's Rule:

A -- T C
-- G
T -- A G --
C

Because A and T always go together and C and G always go together, if you're missing one half of the DNA it can easily be rebuilt by checking out the other half. In fact, this is how DNA reproduces.

Friday 11/14/08

Today in class we took a Quick Quiz, reviewing Photosynthesis and Cellular Respiration.
(I cannot stress how important these two cellular processes are! They are absolutely essential to all life on the planet, and will accordingly make up a big chunk of your upcoming Unit Test! Yikes! :-O Study, study, study! Come in for tutoring!)

After the Quiz, we reviewed Photosynthesis & Cell Respiration, and played a little game where several attentive students had the opportunity to win mad Wolf Bucks! <::ca-ching!!!::> $$$
Then we moved on to Cell Division & Mitosis. We reviewed vocab from last time, as well as the mneumonic/acronym memory device "I-P-MAT-C."

We watched a FLASH animation of Mitosis on CellsAlive.com...
...and compared it to another animation of Mitosis found here.
Lastly, we watched real-life video footage of Mitosis happening in a real-life cell! "Wowie-wee! Neato-mosquito! Cool beans & rice!"

Then we closed out class by working on a Guided Notes worksheet, drawing and describing I-P-MAT-C "-phases" of Mitosis, and I told you a little story about Pro-Wrestlers to help you remember the steps of Mitosis that I found here.

HOMEWORK: Finish the Guided Notes worksheet. Study, study for upcoming Exam (before Thanksgiving Break!) If you missed, you need to make-up the Quiz and get the handout. Next time I'll stamp your Guided Notes for a grade and collect your Radio K-C-E-L sports announcer worksheet.

Congratulations to our Wolf Buck winners, and I hope to see you all tonight at the Homecoming Dance!!!