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| What important discovery did Griffith make in his pneumonia experiments on mice? | He discovered that there was a transformation in which one strain of bacteria (a harmless strain) was somehow changed permanently into another (the disease causing strain). He hypothesized that the transforming factor might be a gene because the ability to cause disease ws inherited by the transformed bacteria's offspring. |
| Exactly what did Griffith do to the mice in the experiment where he learned about transformation? | He injected mice with his heat-killed, disease-causing bacteria (the heated ones that killed the bacteria) with live, harmless ones. (see 288) So, the harmless bacteria had been transformed into disease-causing genes. |
| What did Avery and his colleagues determine caused the transformation of harmless bacteria into disease causing bacteria? | They found that nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next. |
| What is a bacteriophage? | It is a virus that infects and kills bacteria. (It means "bacteria eater".) |
| Of what are bacteriophage made? | They're made of a DNA or RNA core and a protein coat. |
| What happens when a bacteriophage enters a bacterium? | It attaches to the surface of the cell and inject its viral genetic information into the cell. These viral genes produce many new bacteriophages that gradually destroy the bacterium. When that cell splits, hundreds of new viruses are released. |
| What were Hershey and Chase trying to determine in their experiments? | They wanted to know whether the protein coat or the DNA core of the virus entered the infected cell; this would help them determine whether genes were made up protein or of DNA. |
| What technique did Hershey and Chase use to study the viruses in their experiments? | They used radioactive isotopes of phosphorus-32 and sulfur-35 as markers so they could trace the proteins and DNA to see what they were doing to the cell. |
| Why were phosphorus-32 and sulfur-35 perfect for what Hershey & Chase were investigating in their experiments? | They were perfect because proteins contain almost no phosphorus and DNA contains no sulfur, so the radioactive isotopes would show up in the cells if the phosphorus-32 or sulfur-35 appeared. If sulfur-35 showed up in the bacteria, it meant the viruses' protein had been injected into the bacteria; if the phosphorus-32 was found in the bacteria, the DNA had been injected into the bacteria. |
| What conclusion did Hershey & Chase make regarding the genetic material that was in bacteriophage? | They concluded that the genetic material of the bacteriophage was DNA, NOT protein. |
| What 3 things do genes do that interested scientists? | 1) genes had to carry information from 1 generation to the next; 2) they put that information to work by determining the heritable characteristics of organisms; 3) genes had to be easily copied because all of a cell's genetic information is replicated every time a cell divides. |
| What are nucleotides? | They are the monomers of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base (see 291). |
| What are the 4 kinds of nitrogenous bases in DNA? | 1) adenine & 2) guanine (both are purines); 3) cytosine and 4) thymine (pyrimidines). |
| What is the big difference between the structure of purines and pyrimidines? | Purines have 2 rings in their structure (pg. 291); pyrimidines have one ring (picture on 291). |
| What is the "backbone" of a DNA chain? | Sugar and phosphate are the backbone of a DNA chain. |
| What do Chargaff's Rules say? | In any sample of DNA, the percentages of guanine (G) & cytosine (C) bases were almost equal; the same was true of the percentages of adenine (A) and thymine (T). So, [A] = [T] and [G] = [C] |
| What method did Rosalind Franklin use in her study of DNA? | She used X-ray diffraction, aiming a powerful X-ray beam at concentrated DNA samples and recorded the scattering pattern of the S-rays on film. |
| What important clues re: DNA arose from Franklin's work? | 1) The X-shaped pattern shows that the strands in DNA are twisted around each other in a shape known as a helix; 2) the angle of the X suggested there are 2 strands in the structure; 3) the nitrogenous baes are near the center of molecule. |
| What breakthrough did Watson & Crick make? | They made a model of DNA showing a double helix, in which 2 strands were wound around each other. They also discovered that hydrogen bonds could form between certain nitrogenous bases and provide enough force to hold the 2 strands together. |
| What is "base pairing"? | Watson & Crick found that For every adenine in a double-stranded DNA molecule, there had to be exacly one thymine molecule; for each cytosine molecule, there was one guanine molecule. |
