Chapter 8 Biochemistry

question

The compound that consists of ribose linked by an N-glycosidic bond to N-9 of adenine is: A) a deoxyribonucleoside. B) a purine nucleotide. C) a pyrimidine nucleotide. D) adenosine monophosphate. E) adenosine.
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E) adenosine.
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A major component of RNA but not of DNA is: A) adenine. B) cytosine. C) guanine. D) thymine. E) uracil.
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E) uracil.
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The difference between a ribonucleotide and a deoxyribonucleotide is: A) a deoxyribonucleotide has an —H instead of an —OH at C-2. B) a deoxyribonucleotide has alpha configuration; ribonucleotide has the beta configuration at C-1. C) a ribonucleotide has an extra —OH at C-4. D) a ribonucleotide has more structural flexibility than deoxyribonucleotide. E) a ribonucleotide is a pyranose, deoxyribonucleotide is a furanose.
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A) a deoxyribonucleotide has an —H instead of an —OH at C-2.
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Which one of the following is true of the pentoses found in nucleic acids? A) C-5 and C-1 of the pentose are joined to phosphate groups. B) C-5 of the pentose is joined to a nitrogenous base, and C-1 to a phosphate group. C) The bond that joins nitrogenous bases to pentoses is an O-glycosidic bond. D) The pentoses are always in the β-furanose forms. E) The straight-chain and ring forms undergo constant interconversion.
answer

D) The pentoses are always in the β-furanose forms.
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The phosphodiester bonds that link adjacent nucleotides in both RNA and DNA: A) always link A with T and G with C. B) are susceptible to alkaline hydrolysis. C) are uncharged at neutral pH. D) form between the planar rings of adjacent bases. E) join the 3′ hydroxyl of one nucleotide to the 5′ hydroxyl of the next.
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E) join the 3′ hydroxyl of one nucleotide to the 5′ hydroxyl of the next.
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The phosphodiester bond that joins adjacent nucleotides in DNA: A) associates ionically with metal ions, polyamines, and proteins. B) is positively charged. C) is susceptible to alkaline hydrolysis. D) Links C-2 of one base to C-3 of the next. E) links C-3 of deoxyribose to N-1 of thymine or cytosine.
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A) associates ionically with metal ions, polyamines, and proteins.
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The alkaline hydrolysis of RNA does not produce: A) 2′- AMP. B) 2′,3′-cGMP. C) 2′-CMP. D) 3′,5′-cAMP. E) 3′-UMP.
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D) 3′,5′-cAMP.
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The DNA oligonucleotide abbreviated pATCGAC: A) has 7 phosphate groups. B) has a hydroxyl at its 3’end. C) has a phosphate on its 3′ end. D) has an A at its 3′ end. E) violates Chargaff’s rules.
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B) has a hydroxyl at its 3’end.
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For the oligoribonucleotide pACGUAC: A) the nucleotide at the 3′ end has a phosphate at its 3′ hydroxyl. B) the nucleotide at the 3′ end is a purine. C) the nucleotide at the 5′ end has a 5′ hydroxyl. D) the nucleotide at the 5′ end has a phosphate on its 5′ hydroxyl. E) the nucleotide at the 5′ end is a pyrimidine.
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D) the nucleotide at the 5′ end has a phosphate on its 5′ hydroxyl.
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The nucleic acid bases: A) absorb ultraviolet light maximally at 280 nm. B) are all about the same size. C) are relatively hydrophilic. D) are roughly planar. E) can all stably base-pair with one another.
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D) are roughly planar.
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Which of the following statements concerning the tautomeric forms of bases such as uracil is correct? A) The all-lactim form contains a ketone group. B) The lactam form contains an alcohol group. C) The lactam form predominates at neutral pH. D) They are geometric isomers. E) They are stereoisomers.
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C) The lactam form predominates at neutral pH.
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In a double-stranded nucleic acid, cytosine typically base-pairs with: A) adenosine. B) guanine. C) inosine. D) thymine. E) uracil.
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B) guanine
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In the Watson-Crick model for the DNA double helix (B form) the A-T and G-C base pairs share which one of the following properties? A) The distance between the two glycosidic (base-sugar) bonds is the same in both base pairs, within a few tenths of an angstrom. B) The molecular weights of the two base pairs are identical. C) The number of hydrogen bonds formed between the two bases of the base pair is the same. D) The plane of neither base pair is perpendicular to the axis of the helix. E) The proton-binding groups in both base pairs are in their charged or ionized form.
answer

A) The distance between the two glycosidic (base-sugar) bonds is the same in both base pairs, within a few tenths of an angstrom
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The experiment of Avery, MacLeod, and McCarty in which nonvirulent bacteria were made virulent by transformation was significant because it showed that: A) bacteria can undergo transformation. B) genes are composed of DNA only. C) mice are more susceptible to pneumonia than are humans. D) pneumonia can be cured by transformation. E) virulence is determine genetically.
answer

B) genes are composed of DNA only.
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Chargaff’s rules state that in typical DNA: A) A = G. B) A = C. C) A = U. D) A + T = G + C. E) A + G = T + C.
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E) A + G = T + C.
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Based on Chargaff’s rules, which of the following are possible base compositions for double-stranded DNA? %A %G %C %T %U A) 5 45 45 5 0 B) 20 20 20 20 20 C) 35 15 35 15 0 D) all of the above E) none of the above
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A) 5 45 45 5 0
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In the Watson-Crick structure of DNA, the: A) absence of 2′-hydroxyl groups allows bases to lie perpendicular to the helical axis. B) adenine content of one strand must equal the thymine content of the same strand. C) nucleotides are arranged in the A-form. D) purine content (fraction of bases that are purines) must be the same in both strands. E) two strands are parallel.
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A) absence of 2′-hydroxyl groups allows bases to lie perpendicular to the helical axis.
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In the Watson-Crick model of DNA structure: A) both strands run in the same direction, 3′ to 5′; they are parallel. B) phosphate groups project toward the middle of the helix, where they are protected from interaction with water. C) T can form three hydrogen bonds with either G or C in the opposite strand. D) the distance between the sugar backbone of the two strands is just large enough to accommodate either two purines or two pyrimidines. E) the distance between two adjacent bases in one strand is about 3.4 Å.
answer

E) the distance between two adjacent bases in one strand is about 3.4 Å.
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Which of the following is not true of all naturally occurring DNA? A) Deoxyribose units are connected by 3′,5′-phosphodiester bonds. B) The amount of A always equals the amount of T. C) The ratio A+T/G+C is constant for all natural DNAs. D) The two complementary strands are antiparallel. E) Two hydrogen bonds form between A and T.
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C) The ratio A+T/G+C is constant for all natural DNAs.
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In the Watson-Crick model of DNA structure (now called B-form DNA): A) a purine in one strand always hydrogen bonds with a purine in the other strand. B) A-T pairs share three hydrogen bonds. C) G-C pairs share two hydrogen bonds. D) the 5′ ends of both strands are at one end of the helix. E) the bases occupy the interior of the helix.
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E) the bases occupy the interior of the helix
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The double helix of DNA in the B-form is stabilized by: A) covalent bonds between the 3′ end of one strand and the 5′ end of the other. B) hydrogen bonding between the phosphate groups of two side-by-side strands. C) hydrogen bonds between the riboses of each strand. D) nonspecific base-stacking interaction between two adjacent bases in the same strand. E) ribose interactions with the planar base pairs.
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D) nonspecific base-stacking interaction between two adjacent bases in the same strand.
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In nucleotides and nucleic acids, syn and anti conformations relate to: A) base stereoisomers. B) rotation around the phosphodiester bond. C) rotation around the sugar-base bond. D) sugar pucker. E) sugar stereoisomers.
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C) rotation around the sugar-base bond
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B-form DNA in vivo is a ________-handed helix, _____ Å in diameter, with a rise of ____ Å per base pair. A) left; 20; 3.9 B) right; 18; 3.4 C) right; 18; 3.6 D) right; 20; 3.4 E) right; 23; 2.6
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D) right; 20; 3.4
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In double-stranded DNA: A) only a right-handed helix is possible. B) sequences rich in A-T base pairs are denatured less readily than those rich in G-C pairs. C) the sequence of bases has no effect on the overall structure. D) the two strands are parallel. E) the two strands have complementary sequences.
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E) the two strands have complementary sequences.
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Which of the following is a palindromic sequence? A) AGGTCC TCCAGG B) CCTTCC GCAAGG C) GAATCC CTTAGG D) GGATCC CCTAGG E) GTATCC CATAGG
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D) GGATCC CCTAGG
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Triple-helical DNA structures can result from Hoogsteen (non Watson-Crick) interactions. These interactions are primarily: A) covalent bonds involving deoxyribose. B) covalent bonds involving the bases. C) hydrogen bonds involving deoxyribose. D) hydrogen bonds involving the bases. E) hydrophobic interactions involving the bases.
answer

D) hydrogen bonds involving the bases
question

Which of the following are possible base compositions for single-stranded RNA? %A %G %C %T %U A) 5 45 45 0 5 B) 25 25 25 0 25 C) 35 10 30 0 25 D) all of the above E) none of the above
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D) all of the above
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Double-stranded regions of RNA: A) are less stable than double-stranded regions of DNA. B) can be observed in the laboratory, but probably have no biological relevance. C) can form between two self-complementary regions of the same single strand of RNA. D) do not occur. E) have the two strands arranged in parallel (unlike those of DNA, which are antiparallel).
answer

C) can form between two self-complementary regions of the same single strand of RNA.
question

When double-stranded DNA is heated at neutral pH, which change does not occur? A) The absorption of ultraviolet (260 nm) light increases. B) The covalent N-glycosidic bond between the base and the pentose breaks. C) The helical structure unwinds. D) The hydrogen bonds between A and T break. E) The viscosity of the solution decreases.
answer

B) The covalent N-glycosidic bond between the base and the pentose breaks.
question

Which of the following deoxyoligonucleotides will hybridize with a DNA containing the sequence (5′)AGACTGGTC(3′)? A) (5′)CTCATTGAG(3′) B) (5′)GACCAGTCT(3′) C) (5′)GAGTCAACT(3′) D) (5′)TCTGACCAG(3′) E) (5′)TCTGGATCT(3′)
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B) (5′)GACCAGTCT(3′)
question

The ribonucleotide polymer (5′)GTGATCAAGC(3′) could only form a double-stranded structure with: A) (5′)CACTAGTTCG(3′). B) (5′)CACUAGUUCG(3′). C) (5′)CACUTTCGCCC(3′). D) (5′)GCTTGATCAC(3′). E) (5′)GCCTAGTTUG(3′).
answer

D) (5′)GCTTGATCAC(3′).
question

In comparison with DNA-DNA double helices, the stability of DNA-RNA and RNA-RNA helices is: A) DNA-DNA > DNA-RNA > RNA-RNA. B) DNA-DNA > RNA-RNA > DNA-RNA. C) RNA-DNA > RNA-RNA > DNA-DNA. D) RNA-RNA > DNA-DNA > DNA-RNA. E) RNA-RNA > DNA-RNA > DNA-DNA.
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E) RNA-RNA > DNA-RNA > DNA-DNA.
question

In the laboratory, several factors are known to cause alteration of the chemical structure of DNA. The factor(s) likely to be important in a living cell is (are): A) heat. B) low pH. C) oxygen. D) UV light. E) both C and D.
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E) both C and D.
question

Compounds that generate nitrous acid (such as nitrites, nitrates, and nitrosamines) change DNA molecules by: A) breakage of phosphodiester bonds. B) deamination of bases. C) depurination. D) formation of thymine dimers. E) transformation of A to T.
answer

B) deamination of bases.
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In DNA sequencing by the Sanger (dideoxy) method: A) radioactive dideoxy ATP is included in each of four reaction mixtures before enzymatic synthesis of complementary strands. B) specific enzymes are used to cut the newly synthesized DNA into small pieces, which are then separated by electrophoresis. C) the dideoxynucleotides must be present at high levels to obtain long stretches of DNA sequence. D) the role of the dideoxy CTP is to occasionally terminate enzymatic synthesis of DNA where Gs occur in the template strands. E) the template DNA strand is radioactive.
answer

D) the role of the dideoxy CTP is to occasionally terminate enzymatic synthesis of DNA where Gs occur in the template strands.
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In the chemical synthesis of DNA: A) the dimethoxytrityl (DMT) group catalyzes formation of the phosphodiester bond. B) the direction of synthesis is 5′ to 3′. C) the maximum length of oligonucleotide that can be synthesized is 8-10 nucleotides. D) the nucleotide initially attached to the silica gel support will become the 3′ end of the finished product. E) the protecting cyanoethyl groups are removed after each step.
answer

D) the nucleotide initially attached to the silica gel support will become the 3′ end of the finished product.
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In living cells, nucleotides and their derivatives can serve as: A) carriers of metabolic energy. B) enzyme cofactors. C) intracellular signals. D) precursors for nucleic acid synthesis. E) all of the above.
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E) all of the above.
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The “energy carrier” ATP is an example of a(n): A) deoxyribonucleoside triphosphate B) di-nucleotide C) peptide D) ribonucleotide E) ribonucleoside triphosphate
answer

E) ribonucleoside triphosphate

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