2. Cell Chemistry & Cell Components

Nucleic Acids

Textbook Question
Enzymes that break down DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes?a. The two strands of the double helix would separate.b. The phosphodiester linkages of the polynucleotide backbone would be broken.c. The pyrimidines would be separated from the deoxyribose sugars.d. All bases would be separated from the deoxyribose sugars.
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Textbook Question
If nucleotides from the DNA of a human were quantified and 30 percent of them contained the base adenine, what percentage of them would contain the base guanine?a. 20 percentb. 30 percentc. 40 percentd. 70 percent
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Textbook Question
Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA?a. 5′-AGCT-3′ with 5′-TCGA-3′b. 5′-GCGC-3′ with 5′-TATA-3′c. 5′-ATGC-3′ with 5′-GCAT-3′d. All of these pairs are correct.
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Textbook Question
A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacturea. DNA.b. proteins.c. cellulose.d. sucrose.
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Textbook Question
What would be the sequence of the strand of DNA that is made from the following template: 5′-GATATCGAT-3′? (Your answer must be written 5'→3'.) How would the sequence be different if RNA were made from this DNA template?
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Textbook Question
According to the RNA world model, a ribozyme would replicate by creating a double-stranded RNA intermediate. Would you expect the intermediate to have the same catalytic activity as the original ribozyme? Justify your answer with an explanation.
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Textbook Question
Make a concept map (see BioSkills 12) that relates DNA's primary structure to its secondary structure. Your diagram should include deoxyribonucleotides, base-stacking interactions, purines, pyrimidines, phosphodiester linkages, DNA's primary structure, DNA's secondary structure, complementary base pairing, and antiparallel double helix.
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Textbook Question
RNA and DNA are similar because .a. both are double-stranded helices;b. uracil is found in both of them;c. both contain the sugar deoxyribose;d. both are made up of nucleotides consisting of a sugar, a phosphate, and a base
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Textbook Question
DRAW IT Copy the polynucleotide strand in Figure 5.23a and label the bases G, T, C, and T, starting from the 5′ end. Assuming this is a DNA polynucleotide, now draw the complementary strand, using the same symbols for phosphates (circles), sugars (pentagons), and bases. Label the bases. Draw arrows showing the 5'→3' direction of each strand. Use the arrows to make sure the second strand is antiparallel to the first. Hint: After you draw the first strand vertically, turn the paper upside down; it is easier to draw the second strand from the 5′ toward the 3′ direction as you go from top to bottom.
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Textbook Question
In the field of nanotechnology, DNA is used like Velcro to assemble tiny particles into structures that are < 0.0001 mm in size. Draw a model to illustrate how two particles (a circle and a square) could be brought together by linking them to short single-stranded DNA molecules. If the DNA sequence linked to the circle is GGATC, then provide the sequence linked to the square and identify the 5′ and 3′ ends of each strand.
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Textbook Question
Explain the role of complementary base pairing in the functions of nucleic acids.
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Textbook Question
Which of the following is not part of a nucleotide?
a. An amino acid
b. A nitrogenous base
c. One or more phosphate groups
d. A sugar
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Textbook Question
Mark the following properties as belonging to either DNA or RNA.

a. Contains the nucleotides A, G, C, and U _________
b. Found only in the nucleus of the cell   _________
c. Can move in and out of the cell's nucleus _________
d. Contains two strands of nucleotides linked by hydrogen bonds _________
e. Contains the code for every protein in the body _________
f. Contains the sugar ribose _________
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Textbook Question
The drug methotrexate is used to treat several different types of cancer and diseases of the immune system. It works by inhibiting an enzyme in the cell necessary for folic acid synthesis. Without folic acid, the cell cannot make nucleotides. What, specifically, does an enzyme do in the cell? Why would inhibiting this enzyme disrupt folic acid synthesis? What effect would a disruption in folic acid synthesis have on the cell as a whole? (Hint: Think about the role that folic acid plays in the cell.) (Connects to Chapter 2)
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