BIOL 213 1st Edition Exam # 3 Study Guide Lectures: 13 -18Lecture 13 What is the basic structure of DNA? How is it stabilized? Draw it.DNA is a double helix. It’s stabilized by hydrogen bonds between the base pairs and by hydrophobic interactions and Van der Waals interactionsWhat characteristics of the bonds of DNA allow it to be “unzipped”?The covalent bonds that hold the single strand together are a lot stronger than the hydrogen bonds that hold the base pairs of the two strands together, therefore, when force is applied to the strand to pull it apart, the hydrogen bonds break first.Why are the C-G connections more stable than A-T?There are three hydrogen bonds between cytosine and guanine versus only two between adenine and thymine, therefore making the C-G bond stronger and more stable.How is this involved in the origin of replication?It contains more A-T bonds because they’re easier to pull apart.Briefly describe Frederick Griffith’s experiment.He tested two types of pneumonia bacteria and their effect on mice. He had S-strand and R-strand bacteria. The S-strand bacteria produced a large amount of carbohydrates that coated the surface of the cell; the R-strain did not. When he injected the S-strain into a mouse, it died. When he injected the R-strain into a mouse, it lived. When he heat killed S-strain bacteria and injected it into a mouse, it lived. When he mixed R-strain bacteria and heat killed S-strain bacteria and injected it into a mouse, it died.What advantage did the carbohydrate coating give the S-strain?The coating made the bacteria more slippery so that the mouse’s immune cells weren’t able to grab onto it to kill it.How did this experiment help in the discovery that DNA is the genetic material?Griffith discovered transformation. This meant that genetic information was somehow transferred from the dead S-strain bacteria to the live R-strain. People now knew that the genetic material could be passed to a different cell and what experiment to do in order to find out what the genetic material was.Briefly describe Avery, MacLeod, and McCarty’s experiment.They took S-strain bacteria and heat-killed in. In one experiment, they fractionalized it into its macromolecules (RNA, DNA, lipids, proteins and carbohydrates) and added these one at a time to R-strain bacteria to see which one would cause it to create carbohydrates. They found that DNA did this. In the other experiment, they added the S-strain bacteria to R-strain and broke down each S-strain’s macromolecules one at a time with corresponding enzymes to see after which molecule was broken down, the R-strain stop producing carbohydrates. It stopped producing carbohydrates after the DNA was broken down.What enzymes were used to break down which macromolecule?RNase for RNA. Protease for proteins. DNase for DNA. Lipase for lipids. Amylase for carbohydrates.They used protease to break down proteins in the second experiment. Where can proteases be found in the cell? They are found in proteasomes. These contain the enzyme, which breaks down proteins that are no longer needed by the cell.Briefly describe the Hershey-Chase experiment. Draw it.They used bacteriophages, which they knew were only composed of protein and DNA, and let them inject bacteria so that they could figure out which one was the genetic material. They labeled the viral DNA with 32P and the viral protein with 35S. After they added the bacteriophages to the bacteria solution and allowed them to infect the bacteria, they centrifuged the solution to get rid of the protein capsules. They then analyzed the solution to see if it contained 32P or 35S. They found 35P, which meant that the DNA was injected into the cell,which meant that DNA was the genetic material.Why was DNA labeled with phosphorus and proteins with nitrogen?The DNA backbone contains a phosphate group and proteins contain nitrogen in the amine group.What was Chargaff’s contribution to the understanding of DNA?He discovered that different organisms contain different relative levels of cytosine and guanine to adenine and thymine, but that all organisms contain the same relative levels of cytosine to guanine and adenine to thymine. The amount of adenine would always equal the amount of thymine, and the amount of cytosine would always equal the amount of guanine.Briefly describe Watson and Crick’s experiment. They analyzed the x-ray crystallography data of Rosalind Franklin and were able to discover the double-helical structure of DNA. They discovered that A pairs with T and that C pairs with G. They discovered that A and T bond via two hydrogen bonds while C and G bond via three hydrogen bonds.How does the structure of DNA allow it to replicate?It contains complementary strand, therefore allowing one strand to be the template of the other. The fact that the base pairs are joined by hydrogen bonds allows the moleculeto be pulled apart into its separate strands.What is the central dogma of biology? What are the molecules associated with each process?How does the cell deal with the massive amount of DNA?It organizes it into denser structures.In what process are chromosomes important? Why?Mitosis. It would be really hard for the cell to separate the chromosomes into two cells ifit weren’t compact.What’s the first step of DNA compaction? What protein is involved? Draw it.The DNA wraps around histone proteins. Each histone is made up of 8 subunits. Histone + DNA = nucleosomeWhat property of histones allows the DNA to be tightly bound to it?They are positively charged which causes them to be highly attracted to the negatively charged DNA.How can histones be an issue when it comes to DNA replication or transcription? What are some proteins that can solve this issue?They can physically block the necessary proteins from binding to the DNA. Histone remodeling complexes can loosen the DNA from the histones, let the proteins reach the DNA, and then tighten it again.LECTURE 14Base pairs are always added to the 3’ end of DNA. What does it mean when one end is 5’ and one is 3’?The 5’ end is the end of the DNA strand that has the phosphate group. The phosphorus atom is bonded to the 5’ carbon of the (in the case of DNA) deoxyribose sugar. The 3’ end is the end of the DNA strand that has an –OH group bonded to the 3’ carbon of the deoxyribose sugar.What does it mean when the 5’ end is attached to the