Module+Three+Review

[] [] This picture above shows Hershey and Chase (say that 5 times fast). I would like you to use the links above and your text and your workbook to get ready to talk about this experiment. Draw a diagram and explain the experimental procedure.

What were the key results of the Hershey Chase Experiment? When bacteriophagescontaining 32p(radioactive), were allowed to infect nonradioactive bacteria, all the infected cells became radioactive and, in fact much of the radioactivity was passed on to the next generation of bateriophages. However when the bacteria were infected with bacteriophages labeled with 35s, and then the virus coats removed, practically no radioactivity could be detected in the effected cells.

What did these results tell scientists about the nature of the genetic material? That the transformation was permanently heritable. Even after a few hunred generations, S cell descenddants were still infectious.

Know the other scientists and their work leading up to Watson and Crick: Miescher ﻿- **discovered a microscopic substance in the pus of discarded surgical bandages. He freed nuclei from cell.** Griffith**- discovered that traits of the smooth form of pneumococcus could be transfered to the rough form of the same bacteria by mixing killed smooth bacteria with the live rough form.** Avery/McCarty**- discovered that DNA is the substance that causes bacterial transformation.** Franklin- **developed a refined x-ray diffraction method. She took the first photograph of DNA.** 2. Replication Bubble. [] This is a picture of a bubble of replication. You should be able to draw something like this. Also be able to label and above (3’, 5’, lagging strand, leading strand, direction DNA polymerase reads, and helicase. Also, add where DNA Ligase would work and the origin of replication.

3. How did Watson and Crick figure out the exact configuration of the base pairing on the DNA double helix? They used information from Rosalind Franklin and focused on what she reported on. They had got the final bit of information that they needed to build a plausiable model of DNA- one with two helically twisted chains running in opposing directions.

Remember our discussion in class. 1. Hydrogen bonds between bases allows for easy unzipping, rezipping; 2. A=T, G=C according to Chargaff’s rules; 3. Purine must hook up with pyrimidine to keep the constant diameter of the double helix; 4. 2 bonds between A-T, 3 H-bonds between G-C.

I like the question in your workbook pg. 12: Give two reasons why in DNA replication, the nucleotides T always pairs with A and Cytosine always pairs with Guanine.

First, the amount of adenine relative to guanine differs among species. Second, the amounts of thymine and adanine in DNA are identical, and so are the amounts of cytosine and guanine.
 * - Purines are larger than pyramidines and two of them would not fit together on one "rung" of the DNA ladder. **
 * -Adenine cannot form a hydrogen bond with cytosine and thymine cannot form a hydrogen bond with guanine. **
 * - The purine base with two hydrogen bonding sites matches up with the pyrimidine base that has two corresponding hydrogen bonding sites (A and T) **
 * -The purine base with 3 hydrogen bonding sites matches up with the pyrimidine base that has 3 corresponding hydrogen bonding sites (C and G). **

4. Describe 4 differences between the structures of a DNA and RNA molecule. (see page 5 in your workbook).

5. List the enzymes used in DNA replication and the enzymes used in Transcription/Translation. Tell the role of each enzyme and tell which direction they may proceed? Either direction or one way only.

6. Know the changes that a newly transcribed RNA molecule undergo before export from the nucleus as a fully functioning mRNA. (Cap, Tail, splicing) Draw the changes here and explain.

7. Please study your workbook. Read it over and over and try to make up some questions of your own. 8. Please know everything on the **Review Key Concepts Page** (24 of your workbook). Would you be able to fill this out from memory?

I may just Xerox a couple of pages of your workbook and have you fill them out to see that you have used your workbook and KNOW the workbook on the exam.

Practice drug problems: [] Don’t forget, this exam also has some questions from Chapters 2&3 (arrgh!!!) so don’t forget to review these.