Early researchers expected the genetic material to be protein rather than DNA because
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proteins have more than 20 different monomers, while DNA has only 4; DNA just seemed too simple to carry complex genetic instructions.
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they hadn't yet found any DNA inside nuclei, only proteins.
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nucleic acids seemed simple, repetitive, and uninteresting, compared to proteins.
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with their almost limitless variation in structure and function, proteins seemed complex enough to contain genetic information.
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Question 2 Avery, MacLeod, and McCarty demonstrated that DNA alone was enough to transform (i.e., change the phenotypes of)Staphylococcus pneumoniae by
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showing that if S strain DNA was destroyed using a DNAase, the R-strain would not become virulent because the R-strain DNA had been destroyed.
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using an enzyme that destroyed S strain RNA; R cells that received this solution became virulent.
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showing that if S strain DNA was destroyed using a DNAase, the R strain would not become virulent because the genes for the protective polysaccharide capsule were destroyed.
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using an enzyme that destroyed S strain proteins; R-stain cells that received this solution did not become virulent.
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Question 3 Avery, McCloud, & McCarty supported Griffith's conclusions with their own experiments in 1944
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by showing that DNA was the "transforming principle".
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but their work had little impact, in part because few scientists at the time thought that what went on in bacteria was in any way related to processes in more complex life forms.
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but their work convinced most scientists of the time, by showing that DNA was just as complex as protein.
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when they showed that either DNA or protein isolated from the S strain was sufficient to transform the R strain.
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Question 4
The complementary strands that make up a DNA molecule are said to be antiparallel because
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weak hydrogen bonds hold the 2 strands together, while strong covalent bonds bind one nucleotide to the next in the backbone of the molecule.
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the 5' end of one polynucleotide matches up with 3' end of the other.
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each of the nucleotides on one strand is flipped in orientation, relative to the nucleotides on the other strand.
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a purine always matches up with a pyrimidine in pair-bonding.
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Question 5
Erwin Chargaff discovered some regularities about the relative percentages of adenine, guanine, cytosine, and thymine in DNA. Which of the following statements is/are true regarding this topic?
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If DNA from a cell is analyzed, and found to contain 40% adenine, it will also have 10% guanine.
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Fifty percent of the DNA nucleotides will be purines.
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If DNA from a cell is analyzed, and found to contain 40% adenine, it will also have 40% cytosine.
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If DNA from a cell is analyzed, and found to contain 40% adenine, it will also have 20% cytosine.
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