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Exam 4: Nucleic Acids and the Rna World

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Question 21

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Use the following information when answering the corresponding question(s) . Shu-ichi Nakano reported in Science in February 2000 that "the RNA enzyme (ribozyme) from hepatitis delta virus catalyzes self-cleavage of a . . . [chemical] . . . bond." This reaction is inherently slow due to the formation of an unfavorable negative charge on the ribozyme. The author goes on to show that this self-cleavage is made faster by joining it with an acid-base reaction that neutralizes the negative charge. Nakano's model describes a positively charged cytosine base on the ribozyme acting as the acid and magnesium hydroxide acting as the base. Specifically, the cytosine donates its proton (H+) to neutralize the unstable negative charge that would have formed on the ribozyme. -Refer to Nakano's quote from Science. If the cytosine is positively charged (+) before self-cleavage, what would its charge be after self-cleavage?

A) + (positive)
B) − (negative)
C) 0 (neutral)
D) There is no way to predict.

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Question 22

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Which of the following are purine nitrogenous bases?

A) cytosine and guanine
B) guanine and adenine
C) adenine and thymine
D) thymine and uracil
E) uracil and cytosine

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Question 23

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Compare proteins to nucleic acids. Which of the following is TRUE?

The difference between the sugar in DNA and the sugar in RNA is that the sugar in DNA ________.

Recall the Bartel lab group experiment to create a ribozyme from scratch. If they had created exact copies of each ribozyme (rather than creating copies with a few differences) , the ribozymes would have ________.

Which of the following descriptions best fits the class of molecules known as nucleotides?

Nucleic acids have a definite polarity, or directionality. Stated another way, one end of the molecule is different from the other end. How are these ends described?

What is the difference (if any) between the structure of ATP and the structure of the precursor of the A nucleotide in RNA?

Use the following information when answering the corresponding question(s) . Shu-ichi Nakano reported in Science in February 2000 that "the RNA enzyme (ribozyme) from hepatitis delta virus catalyzes self-cleavage of a . . . [chemical] . . . bond." This reaction is inherently slow due to the formation of an unfavorable negative charge on the ribozyme. The author goes on to show that this self-cleavage is made faster by joining it with an acid-base reaction that neutralizes the negative charge. Nakano's model describes a positively charged cytosine base on the ribozyme acting as the acid and magnesium hydroxide acting as the base. Specifically, the cytosine donates its proton (H+) to neutralize the unstable negative charge that would have formed on the ribozyme. -Is Nakano's quote from Science consistent with the textbook's claim that RNA is a good candidate for the first life-form?

RNA and proteins combine in cells to form structures called ribosomes. Ribosomes contain the active site for peptide bond formation. Based on their chemical structures, do you think protein or RNA molecules actually form the active site within the ribosome?

If 14C-labeled uracil is added to the growth medium of cells, what macromolecules will be labeled?

Use the following information when answering the corresponding question(s) . Shu-ichi Nakano reported in Science in February 2000 that "the RNA enzyme (ribozyme) from hepatitis delta virus catalyzes self-cleavage of a . . . [chemical] . . . bond." This reaction is inherently slow due to the formation of an unfavorable negative charge on the ribozyme. The author goes on to show that this self-cleavage is made faster by joining it with an acid-base reaction that neutralizes the negative charge. Nakano's model describes a positively charged cytosine base on the ribozyme acting as the acid and magnesium hydroxide acting as the base. Specifically, the cytosine donates its proton (H+) to neutralize the unstable negative charge that would have formed on the ribozyme. -Which of the following chemical bonds do you think Nakano is referring to in his quote?

If a double-stranded DNA sample were composed of 10 percent thymine, what would be the percentage of guanine?

Bartel's research group showed that an RNA replicase ribozyme could be created by ________.

Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA?

Some viruses consist only of a protein coat surrounding a nucleic acid core. If you wanted to radioactively label the nucleic acids separately from the protein, you would use radioactive ________.

Franklin and Wilkins analyzed DNA by bombarding DNA crystals with X-rays. Their analysis yielded two numbers that sparked interest, 3.4 nm and 0.34 nm. What is the significance of these numbers?

Nucleic acids are polymers made up of which of the following monomers?

DNA is the main hereditary material of all life. However, DNA lacks one important characteristic for the first forms of life. Why have researchers rejected the idea that DNA was found in the first life-form?

Which of the following statements best summarizes the differences between DNA and RNA?