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UHD BIOL 3303 - Exam 1 Study Guide

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BIOL 3303 1st Edition Exam #1 Study Guide Chapters 9- 10All photos and figures from lecture notes and supplementary text, Principles of Genetics, Sixth Edition by Snustad and Simmons. Questions from Spring 2015 study guides provided by the instructor, Kang.Chapter 9DNA and the Molecular Structure of Chromosomes1. Describe the criteria of genetic material and how DNA matches these criteria.a. Storage of information – DNA stores genetic info in the sequence of nucleotide basesb. Variation between individuals – mutations occur between generations, affecting genotypes and phenotypes from one generation to the nextc. Replication – DNA is replicated semi-conservatively, producing genetic copies of itself to pass on to the next generation of cellsd. Function in expression – DNARNAPROTEINS which functiondirectly to express a phenotype(s)e. Relatively stable (not necessary for infectious agents) – relative to RNA or proteins, DNA is most stable, owing to numerous hydrogen bonds, covalent linkages, and its durability in comparison.2. Explain in general terms why both DNA and proteins were candidatesfor being genetic material.a. Proteins and DNA both performed most of the major required functions of genetic material;These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.i. Proteins also store info, within the sequence of amino acidsii. Proteins also show variation, in that mutations caused differently shaped and differently functioning proteins from what is normally observed in individuals, i.e., sickle celliii. Proteins are not able to replicate themselvesiv. Proteins perform a major role in expression, demonstrating direct expression through their 6 major functions (which are?)v. In comparison to DNA, proteins are not as stable; they are easily denatured by slight changes in temperature or pH3. Explain the three experiments by Griffith, Sia and Dawson, Avery, Hershey and Chase which led to the notion that DNA was the genetic material. Understand experimental designs, results, and interpretations.a. Griffith’s Mice – when heat-killed Type IIIS (virulent when alive) was injected to mice, the mice were unharmed. When live Type IIR bacteria (nonvirulent) was injected, the mice were also unharmed. When both heat-killed Type IIIS and live Type IIR bacteria were injected, the mice developed pneumonia and died.This phenomenon implied the presence of a “transforming agent” which transformed the nonvirulent Type IIR bacteria to virulent Type IIIS, thus killing the injected mice.b. Sia and Dawson in vitro – this experiment was the same as Griffith’s, but without the mice. Instead of injecting mice, Sia and Dawson attempted to grow heat-killedType IIIS and live Type IIR bacteria in separate culture mediums, then together in the same culture medium. The results were the same: when mixed together in the same medium, Type IIR bacteria was transformed into Type IIIS bacteria. This eliminated any suspicion that the mice had something to do with the transformation:Figure 1: Sia and Dawson Experiment.c. Avery and colleagues demonstrated that the “transforming principle” in S. pneumoniae is DNA by using enzymes which degraded either DNA (deoxyribonuclease), RNA (ribonuclease), or proteins (protease) in transforming Type IIR bacterial cells. Neither treatment with protease nor RNase restricted transforming activity; only DNase treatment affected transformation: ALL transforming activity was eliminated:Figure 2: Avery, MacLeod, and McCarty Experiment.d. Hershey and Chase worked with bacteriophage T2 to determine if DNA or proteins carry its genetic information. They “marked” each component in individual experiments: in one experiment, they marked DNA with a radioactive isotope of phosphorus (recall that phosphorus is a key component of DNA) and in the other experiment, they marked the protein coats with radioactive isotope of sulfur (recall that sulfur is a key component of proteins). After the cells were infected, they were sheared in a blender and centrifuged to separate bacteria from phage. In the radioactive phosphorus experiment, radioactivity was in the insides cells, and in the radioactive sulfur experiment, radioactivity was in the supernatant. This indicated that the DNA of the virus enters the host cell, whereas the protein coat remains outside the cell: DNA CARRIES THE GENETIC INFORMATION FOR BACTERIOPHAGE T2:Figure 3: Hershey and Chase Experiment.4. List exceptions to DNA being genetic materiala. RNA is the genetic material in RNA viruses.5. Master the basic features of a B-form DNA as first reported by Watsonand Crick. Be able to list its monomers, the name of linkage that connects monomers, the diameter of the double helix and the number of base pairs (bp) per turn. Be able to draw a DNA structure.a. B-form DNA is a double stranded model of a sequence of nucleotides (made up of a pentose, a phosphate group, and a nitrogenous base) where the sugars and phosphates compose the backbones of the structure, with the bases in the middle, hydrogen-bonded together. These nucleotide are bonded together along the strand with phosphodiester linkages. The structure is a double helix in the right-hand direction with 1.9 nm diameter and 10 bp per turn:Figure 4: Basic structure of DNA Figure 5: Rosalind’s image6. Have the knowledge of the scientists and historical backgrounds behind the DNA structure discovery and explain how each of their work contributes to the model: Linus Pauling, Rosalind Franklin, Chargaff, Watson and Crick. a. Pauling: proposed a model of DNA with 3 helices, with sugar phosphate backbone along the axis and the bases on the outsideb. Franklin: X-ray crystallography which placed base pairs .34 nm apartc. Chargaff: Chargaff’s rules [%adenine=%thymine(or %uracil); %cytosine=%guanine] gave evidence that DNA is double stranded.7. List examples of non-B form DNA and explain how they are different from B-form. Be able to describe the conditions under which each of these structures can form and what biological functions they have. Have some knowledge of the evidence that supports their biological functions and be able to evaluate them when provided.a. A-DNA: right-handed with 11 bp per turn; 2.3 nm diameter; dehydrated environments (high salt concentrations); DNA-RNA or RNA-RNA duplexes exist in a similar structure in


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