Genetics - Analysis and Principles

Biology

Quiz 9 :

Molecular Structure of Dna and Rna

Quiz 9 :

Molecular Structure of Dna and Rna

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What are the building blocks of a nucleotide With regard to the 5 and 3 positions on a sugar molecule, how are nucleotides linked together to form a strand of DNA
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The polymeric nucleic acids, DNA and RNA are made of subunits known as nucleotides. The nucleotides are made of three major building blocks, the nitrogenous bases, the carbon sugar (ribose sugar in RNA and deoxyribose sugar in DNA), and the phosphate group.
The phosphate group is attached to the sugar, which in turn is linked to the nitrogenous base. Several nucleotides with all three building blocks link together to form a DNA strand. The nucleotides link themselves in a specific sequence, in a manner that the DNA strand has a 5' and 3' of the sugar at the opposite ends. The phosphate backbone attaches itself to the 5' end of the sugar and the 3' end of the sugar molecule in turn is linked to another phosphate group. Thus, while the 5' position of the sugar is at one end of the DNA strand, the opposite end will always have the 3' group of a pentose sugar.

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If one DNA strand is 5 -GGCATTACACTAGGCCT-3 , what is the sequence of the complementary strand
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The DNA double helix has a pair of strands that are formed by the complementary base pairing. While guanine on one strand pairs with the cytosine on the complementary strand, the adenine of one strand always pairs with the thymine on the complementary strand. This base pairing specifically between guanine and cytosine and between adenine and thymine is known as the complementary base pairing. Thus, the two strands of the DNA double helix are complementary and opposed, the sequence moving in the opposite direction.
In accordance to the base pair rule, the sequence of the complementary strand to a strand with the sequence 5'-GGCATTACACTAGGCCT-3' would be 3'-CCGTAATGTGATCCGGA-5'.

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Look up the meaning of the word transformation in a dictionary and explain whether it is an appropriate word to describe the transfer of genetic material from one organism to another.
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The synonyms for the word 'transformation' in most dictionaries include 'alteration', 'change', and 'conversion'. The definition for the word 'transformation' in most dictionaries provides the meaning 'to induce a change'.
It is appropriate to describe the process of genetic material transfer from one organism to another as 'transformation' as the transferred genetic material "induces a change" in the recipient.

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The type of model building used by Pauling and Watson and Crick involved the use of ball-and-stick units. Now we can do model building on a computer screen. Even though you may not be familiar with this approach, discuss potential advantages of using computers in molecular model building.
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Draw the structure of guanine, guanosine, and deoxyguanosine triphosphate.
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Gierer and Schramm exposed plant tissue to purified RNA from tobacco mosaic virus, and the plants developed the same types of lesions as if they had been exposed to the virus itself. What would be the results if the RNA was treated with DNase, RNase, or protease prior to its exposure to the plant tissue
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Draw the structure of a phosphodiester linkage.
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With regard to the experiment of Figure 9.5, answer the following: A. Provide possible explanations why some of the DNA is in the supernatant. B. Plot the results if the radioactivity in the pellet, rather than in the supernatant, had been measured. C. Why were 32 P and 35 S chosen as radioisotopes to label the phages D. List possible reasons why less than 100% of the phage protein was removed from the bacterial cells during the shearing process. FIGURE 9.5 Evidence that DNA is the genetic material of T2 bacteriophage. Starting materials: The starting materials were E. coli cells and two preparations of radiolabeled T2 phage. One phage preparation had phage proteins labeled with 35 S, and the other preparation had phage DNA labeled with 32 P. img
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An interesting trait that some bacteria exhibit is resistance to killing by antibiotics. For example, certain strains of bacteria are resistant to tetracycline, whereas other strains are sensitive to tetracycline. Describe an experiment you would carry out to demonstrate that tetracycline resistance is an inherited trait encoded by the DNA of the resistant strain.
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Describe how bases interact with each other in the double helix. This discussion should address the issues of complementarity, hydrogen bonding, and base stacking.
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What is the meaning of the term genetic material
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Does the experiment of Figure 9.5 rule out the possibility that RNA is the genetic material of T2 phage Explain your answer. If it does not, could you modify Hershey and Chase's approach to show that DNA and not RNA is the genetic material of T2 bacteriophage Note: It is possible to specifically label DNA or RNA by providing bacteria with radiolabeled thymine or uracil, respectively. FIGURE 9.5 Evidence that DNA is the genetic material of T2 bacteriophage. Starting materials: The starting materials were E. coli cells and two preparations of radiolabeled T2 phage. One phage preparation had phage proteins labeled with 35 S, and the other preparation had phage DNA labeled with 32 P. img
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How might you provide evidence that DNA is the genetic material in mice
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Genetic material acts as a blueprint for an organism's traits. Explain how Griffith's experiments indicated that genetic material was being transferred to the type R bacteria.
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In this chapter, we considered two experiments-one by Avery, MacLeod, and McCarty and the second by Hershey and Chase-that indicated DNA is the genetic material. Evaluate the strengths and weaknesses of the two approaches. Which experimental approach did you find the most convincing Why
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Try to propose structures for a genetic material that are substantially different from the double helix. Remember that the genetic material must have a way to store information and a way to be faithfully replicated.
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With regard to the experiment described in Figure 9.2, answer the following: A. List several possible reasons why only a small percentage of the type R bacteria was converted to type S. B. Explain why an antibody was used to remove the bacteria that are not transformed. What would the results look like, in all five cases, if the antibody/centrifugation step had not been included in the experimental procedure C. The DNA extract was treated with DNase, RNase, or protease. Why was this done (In other words, what were the researchers trying to demonstrate ) FIGURE 9.2 Experiments of Avery, MacLeod, and McCarty to identify the transforming principle. Samples of Streptococcus pneumoniae cells were either not exposed to a type S DNA extract (experiment 1, left side) or exposed to a type S DNA extract (experiments 2-5). Experiments 3, 4, and 5 also contained DNase, RNase, or protease, respectively. After incubation, the cells were exposed to antibodies, which are molecules that can specifically recognize the molecular structure of macromolecules. In this experiment, the antibodies recognized the cell surface of type R bacteria and caused them to clump together. The clumped bacteria were removed by a gentle centrifugation step. Only the bacteria that were not recognized by the antibody (namely, the type S bacteria) remained in the supernatant. The cells in the supernatant were plated on solid growth media. After overnight incubation, visible colonies may be observed. img
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After the DNA from type S bacteria is exposed to type R bacteria, list all of the steps that you think must occur for the bacteria to start making a capsule.
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With regard to Chargaff's experiment described in Figure 9.13, answer the following: A. What is the purpose of paper chromatography B. Explain why it is necessary to remove the bases in order to determine the base composition of DNA. C. Would Chargaff's experiments have been convincing if they had been done on only one species Discuss. FIGURE 9.13 An analysis of base composition among different DNA samples. Starting material: The following types of cells were obtained: Escherichia coli , Streptococcus pneumoniae , yeast, turtle red blood cells, salmon sperm cells, chicken red blood cells, and human liver cells. img img
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What is meant by the term DNA sequence
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