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Exam 4 Fall 07 Key MCB181R Dr. Jorstad

Exam 4 Fall 07 Key MCB181R Dr. Jorstad - MCB 181R Fall 2007...

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MCB 181R, Fall 2007 Instructor: Dr. S. Jorstad Exam IV v1 key For multiple choice questions (each worth 3 points), bubble all correct answers (there may be more than one); there is a 1 point penalty for incorrect answer choices. For short essays (each worth 5 points): confine your answers to the space provided on the scansheet . Writing outside those margins will adversely affect the machine-scoring of your exam. You may use bulleted points to express yourself, as long as your meaning is clear. 1. In the early 20 th century, scientists were trying to figure out what kind of substance the genetic material in cells was made of. They a. knew that the genetic information resided in the nucleus of cells. * b. knew that the contents of the nucleus consisted primarily of proteins and nucleic acids. * c. figured that genetic information was stored in DNA, rather than proteins, because DNA is much more complex. PROTEINS are more complex, and come in a much wider variety of shapes d. knew that 20 amino acid building blocks of proteins was too small a number of monomers to account for all the variation in genes. No, it was thought that the 4 monomers of DNA was too small a number e. had no idea whether the genetic material was made of carbohydrates, lipids, proteins, nucleic acids, or some other kind of molecule. they had narrowed it down to the proteins and DNA found in the nucleus 2. A number of historic experiments that established what we now know about the structure and function of DNA were presented in class. Which of the following statements is/are correct about this topic? a. Griffith’s experiment demonstrated that whatever determined traits of organisms (such as the ability of one bacterial strain to cause disease) was a physical molecule with mass and substance, that could exist outside cells. * b. Work by Avery, MacLeod and McCarty showing that DNA was the transforming principle was immediately embraced by the scientific community. It was rejected, because scientists weren’t certain bacteria and viruses were even alive, let alone that they modeled processes that could be applied to eukaryotes. c. Hershey and Chase demonstrated that the “transforming principle” was DNA, and not protein. * d. Hershey and Chase mutated viruses by using radioactive chemicals, and then studied the effects of the mutations. see “e” below e. Hershey and Chase used radioactive isotopes to track whether viruses passed on proteins or DNA when they infected bacteria with their genomes. *
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3. Watson and Crick won the Nobel Prize for describing the structure of DNA molecules, including the fact that a. the bases point outward from the center of the double helix They point inward into the interior of the helix b. weak bonds are responsible for maintaining all of the structure of the DNA molecule. covalent (phosphodiester) bonds link nucleotides that make up the polynucleotides c. DNA is a double helix made of two polynucleotide strands, running in opposite directions. * = they are antiparallel
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Exam 4 Fall 07 Key MCB181R Dr. Jorstad - MCB 181R Fall 2007...

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