Biology 1 Exam 3 1 Chapter 5 components 1 Understand the importance of the structure of DNA as well as the chemical nature of all of DNA s The body is very simple in its diversity of molecules For example all energy or ATP in the body comes from the breakdown of the one of the three main macronutrients in the body Protein carbohydrates and lipids These macronutrients can all be broken down into their smaller units called polymers and then to just one of the units called monomers Now to get to the actual question DNA is known as the blueprint of the cell it is what makes every person unique The DNA can be transcribed into different types of proteins and this is called gene expression More on that later DNA is in a class called nucleic acids and there are two of them DNA and RNA DNA is the genetic material of the cell and drives protein production It is called a deoxyribonucleic acid because it lacks an oxygen more on the next question If you look at the DNA you can break it down to its building units called the nucleotides These bases as they are called contain a nitrogenous base a sugar molecule and a phosphate The base can either be a thymine adenine guanine or cytosine 2 Be able to compare and contrast the structures of DNA and RNA The other questions are answered in chapter 16 DNA and RNA differ in the pentose sugar DNA has a deoxyribose and RNA is a ribose sugar what this means is that DNA lacks on oxygen on the sugar Chapter 16 1 What is the genetic material of organisms After many experiments it was proven that DNA was the genetic material and that our DNA is our genetic endowment hereditary information is encoded in the chemical language that is DNA DNA 2 effects the development of our biochemical physiological and behavioral traits How does it pass down from generation to generation Though a process called DNA replication that we will learn about It was thought for a long time that proteins were the genetic material it was thought that nucleic acids were way to uniform and simple to be in charge of such a huge role It might be worth knowing the experiments that made this discovery the first experiment was done by studying bacteria and viruses The first study was done by looking at vaccines for pneumonia When the pathogenic disease causing strain was killed with heat was combined with a non pathogenic strain the mouse still died of pneumonia Why The pathogenic strain was killed Clearly some chemical component caused the new generation of bacteria to be pathogenic so it transformed the new generation This was called transformation Now the task was to identify that chemical that caused the transformation Oswald Avery discovered that DNA was the cause by looking at DNA RNA or proteins He did this by treating the pathogenic cells with chemicals that made the DNA RNA or the proteins inactive and only when the DNA was left active did the transformation occur 2 How was this confirmed Now a study was done by Hersey and Chase looking at bacteriophages viruses that attacked bacteria The phages were made out of a protein capsule with DNA inside the capsule and they work by attacking a cell and taking over that cell s metabolic machinery so that cell is programmed The phage called T2 was made of DNA and protein The T2 would attack a bacteria and turn it into a T2 producing factory but what was responsible for that The DNA or the protein of the to make more viruses T2 This was proven via radioactive staining What this means is that the protein was first stained with radioactive sulfur 35S and this makes it possible for us to follow that radioactive molecule Then the let the virus infect the bacteria and then they took the bacteria and centrifuged it in a test tube This process puts the densest material the cells in the bottom of the test tube So all the cells which contain the material that the virus injected in the cell are on the bottom and the radioactive sulfur was seen in the fluid Meaning that the protein is not what causes the cell to transform into a virus producing factory The test is repeated with 3 radioactive phosphate this is part of the DNA and the radioactive phosphate was seen in the bottom after being centrifuged Proving that DNA was responsible 3 How was the idea of DNA base pairing discovered After DNA was proven to contain the genetic information a fellow named Chargaff did an experiment He already knew that DNA consisted of a nitrogenous base a sugar called deoxyribose and a negative charged phosphate The base can either be adenine thymine guanine or cytosine After analzing many organism s he found that the ratio of A adenine was exactly equal to T thymine or vice versa for C and G This meant that the number of A bases ALWAYS equaled the number of T bases he called this Chargaff s Rule So if you are given a question saying the percent of C bases is 19 9 find the other percent s Since we know that the percent of C and G are equal G must be 19 9 We know that there are four bases and they must equal 100 so doing math 100 19 9 19 9 30 3 So there are 60 2 of T and A s and again they are qual So 30 1 of T 30 1 of A 4 How and what is the structure of DNA So they knew that DNA was the genetic material but what was the structure After an experiment with x ray crystallography Watson and Crick discovered that a DNA strand formed a double helix with another DNA strand Even better was that their model explain Chargaff s Rules perfectly A strand of DNA contains the bases and it hydrogen bonds with a complementary strand containing bases following Chargaff s Rule And the strands were also found to be anti parallel What this means in if there was a strand of bases ATGC then the complementary strand that it hydrogen binds to would be TACG This forms a double helix And they are anti parallel with the strands being defined by a 3 and 5 end So the complimentary strand will be 5 to 3 They proved Chargaff s Rule by seeing that A can t complimentary bind with G or C since they will cause the helix to either be too short or too wide A and G are called the purines and T and C are called the pyridimines After trial and error they saw that a purine can only bind with a pyridimine and Chargaff already proved that A binds with T and vice versa 5 Now to duplication 4 That was the model of DNA but how was it passed down to generations Watson and Crick proposed that the helix was broken apart and each strand was used as a …
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