Work Day

Finish up your DNA model and the pictures required

If that is done, work on anything else that needs to be revised :)


p.s. here is the link for the delicious dessert -- Happy Thanksgiving!

Ghost in your genes

To cement your understanding of DNA structure and to add reasons why it is so vital, we are going to watch "Ghost in your Genes" from NOVA.

Click here for additional information on pbs.org

What is the structure of DNA?

How can we make a model of DNA to show it's structure?

How does DNA replicate?

What does the processes of transcription look like?

Using the materials on the table, create one large polymer of A, T, G, & C (about 100 beads in length).  This is one side of the DNA molecule.  What would the other side look like?  Again, using the materials on the table, create the complementary side of DNA, how might you connect the sides? (take a picture when both sides are together, make sure to label the ends with 5' and 3')

How does the structure of DNA make it a stable molecule?
Can you twist the molecule to show it's helical nature?
Where might the histone proteins be located? (what could you use to model them?) Another picture opportunity -- coiled and histone proteins added
How might the location of the histone proteins affect gene expression?

How will the DNA replicate?  Why might it not start at one end and go to the other? Again, using the materials provided, work with your model to show DNA replication. Picture time again, should be able to see Okazaki fragments (and they need to be explained in your submission) :)

Using your original model (or one of the newly replicated strands), show how TRANSCRIPTION works.  (remember to use a different color for the uracil). Where is your promoter region? How does the process stop? Another picture of this process, please :)

Crash Course Biology (DNA structure and replication)
DNA learning center: How DNA is assembled
Crash Course Biology (DNA, Hot Pockets, & the longest word ever)

From Gene to Protein: A Historical Perspective "Replication of DNA"

What were the three models of DNA replication under investigation in the 1950's?

You should be able to describe and define:
Conservative
Semiconservative
Dispersive

Watch the animation from the DNA learning center to learn more about the three models
http://www.dnalc.org/view/15880-Models-of-DNA-replication.html


Which model, conservative, semiconservative or dispersive is actually how DNA replicates?
Assume you have the following materials in your laboratory.  Design an experiment using these materials.  You must justify your choice of organism and isotopes.  You will share your information on a whiteboard with the group.

1. An experimental organism of your choice
2. Your choice of radioactive isotopes (e.g. ¹⁴C, ¹⁴N, ¹⁵N, ³²P)
3. Test Tubes
4. Food/Growth media for organisms
5. A Centrifuge

This template may help in your design

DON'T GO ANY FURTHER UNTIL WE HAVE DISCUSSED EVERYONE'S BOARDS!!

Meselson & Stahl did an experiment to determine which of the 

models for DNA replication was actually correct

Short animation (from McGrawHill)

DNA from the beginning, Module 20 all about DNA replication and the Meselson Stahl experiment.

Work day

Please make sure that you are in your groups for the following labs, and make sure one person in the group has turned it in

• Exploring the Rate of diffusion lab
• Selective Permeability Lab

And individually 

• work on the questions from the "Secret of Photo 51" video. 

DNA Extraction part deux

Today we will extract DNA from strawberries
How might the strawberry DNA compare to your human DNA that was extracted on Friday?
What is the protocol for extracting the DNA?  

DNA extraction :)

DNA Extraction 
How can DNA, a submicroscopic molecule, be visualized by the naked eye?
What must be done to extract and isolate DNA from human cheek cells?
What can we conclude about the chemical nature of DNA through isolation techniques?

Materials provided:
centrifuge tubes, disposable cups, sports drink, ethyl acohol, pipettes, cell lysis (detergent) solution, meat tenderizer (enzyme)

How will you use the above materials to extract DNA from your cheek cells?

Extracting DNA from Your Cells

Cells from the lining of your mouth come loose easily, so you will be able to collect cells containing your DNA by swishing a liquid around in your mouth. 

To extract DNA from your cells, you will need to separate the DNA from the other types of biological molecules in your cells.  You will be using the same basic steps that biologists use when they extract DNA (e.g. to clone DNA or to make a DNA fingerprint). You will follow these 3 easy steps to extract the DNA:

  Detergent

eNzymes (meat tenderizer)

  Alcohol

Rosalind Franklin "The Secret of Photo 51"

Watch the video "The Secret of Photo 51", be prepared to discuss on Friday.  
Use the video sheet, take notes to answer the questions OUTSIDE of class. (the assignment is posted on Canvas)

More Historical Perspective on DNA: From Gene to Protein

How did scientists discover the source of heritable genetic information?

Hershey-Chase Experiments (1952)
Even though the results of Griffith's transforming factor was DNA, other scientists still tested his idea.  
Watch the animation on the Hershey-Chase Experiment

1. What are the elements that make up a nucleic acid vs. a protein?
2. Why did Hershey and Chase use radioactive sulfer and phosphorus in their experiments?
3. Is DNA or protein the genetic material of a phage T2?
4. What evidence does this experiment give you to support this idea?

Let's review the structure of proteins.
Watch the video from education portal about the four levels of protein structure

Why might Rosalind Franklin's X-ray diffraction photograph have been interpreted as an alpha secondary structure?

Yeast again and moving onto DNA :)

Set up your yeast lab again.  I found that the optimal amount of yeast to sugar to water is 

• 1 g yeast
• 2 g sugar
• 10 mL water

Make at least one of your test tubes this way and then conduct your experiment testing one of the variables discussed.

Moving onto DNA! :)
We are going to go through an animation on DNA from the beginning (DNAFTB), specifically 
Concept 15 -- DNA and proteins are key molecules of the cell nucleus. 
& 
Concept 17 -- A Gene is made of DNA