Biochemistry Chapter 8

Front 1

The compound that consists of ribose linked by an N-glycosidic bond to N-9 of adenine is:

Back 1

A) a deoxyribonucleoside.
B) a purine nucleotide.
C) a pyrimidine nucleotide.
D) adenosine monophosphate.
E) adenosine.

Front 2

A major component of RNA but not of DNA is:

Back 2

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

Front 3

The difference between a ribonucleotide and a deoxyribonucleotide is:

Back 3

A) a deoxyribonucleotide has an —H instead of an —OH at C-2.
B) a deoxyribonucleotide has  configuration; ribonucleotide has the  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.

Front 4

Which one of the following is true of the pentoses found in nucleic acids?

Back 4

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 -furanose forms.
E) The straight-chain and ring forms undergo constant interconversion.

Front 5

The phosphodiester bonds that link adjacent nucleotides in both RNA and DNA:

Back 5

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.

Front 6

The phosphodiester bond that joins adjacent nucleotides in DNA:

Back 6

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.

Front 7

The alkaline hydrolysis of RNA does not produce:

Back 7

A) 2'- AMP.
B) 2',3'-cGMP.
C) 2'-CMP.
D) 3',5'-cAMP.
E) 3'-UMP.

Front 8

The DNA oligonucleotide abbreviated pATCGAC:

Back 8

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.

Front 9

For the oligoribonucleotide pACGUAC:

Back 9

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.

Front 10

The nucleic acid bases:

Back 10

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.

Front 11

Which of the following statements concerning the tautomeric forms of bases such as uracil is correct?

Back 11

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.

Front 12

In a double-stranded nucleic acid, cytosine typically base-pairs with:

Back 12

A) adenosine.
B) guanine.
C) inosine.
D) thymine.
E) uracil.

Front 13

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?

Back 13

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.

Front 14

The experiment of Avery, MacLeod, and McCarty in which nonvirulent bacteria were made virulent by transformation was significant because it showed that:

Back 14

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.

Front 15

Chargaff's rules state that in typical DNA:

Back 15

A) A = G.
B) A = C.
C) A = U.
D) A + T = G + C.
E) A + G = T + C.

Front 16

Based on Chargaff's rules, which of the following are possible base compositions for double-stranded DNA?

Back 16

%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

Front 17

In the Watson-Crick structure of DNA, the:

Back 17

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.

Front 18

In the Watson-Crick model of DNA structure:

Back 18

A) both strands run in the same direction, 3'  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.

Front 19

Which of the following is not true of all naturally occurring DNA?

Back 19

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.

Front 20

In the Watson-Crick model of DNA structure (now called B-form DNA):

Back 20

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.

Front 21

The double helix of DNA in the B-form is stabilized by:

Back 21

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.

Front 22

In nucleotides and nucleic acids, syn and anti conformations relate to:

Back 22

A) base stereoisomers.
B) rotation around the phosphodiester bond.
C) rotation around the sugar-base bond.
D) sugar pucker.
E) sugar stereoisomers.

Front 23

B-form DNA in vivo is a ________-handed helix, _____ Å in diameter, with a rise of ____ Å per base pair.

Back 23

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

Front 24

In double-stranded DNA:

Back 24

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.

Front 25

Which of the following is a palindromic sequence?

Back 25

A) AGGTCC
TCCAGG
B) CCTTCC
GCAAGG
C) GAATCC
CTTAGG
D) GGATCC
CCTAGG
E) GTATCC
CATAGG

Front 26

Triple-helical DNA structures can result from Hoogsteen (non Watson-Crick) interactions. These interactions are primarily:

Back 26

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.

Front 27

Which of the following are possible base compositions for single-stranded RNA?

Back 27

%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

Front 28

Double-stranded regions of RNA:

Back 28

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).

Front 29

When double-stranded DNA is heated at neutral pH, which change does not occur?

Back 29

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.

Front 30

Which of the following deoxyoligonucleotides will hybridize with a DNA containing the sequence (5')AGACTGGTC(3')?

Back 30

A) (5')CTCATTGAG(3')
B) (5')GACCAGTCT(3')
C) (5')GAGTCAACT(3')
D) (5')TCTGACCAG(3')
E) (5')TCTGGATCT(3')

Front 31

The ribonucleotide polymer (5')GTGATCAAGC(3') could only form a double-stranded structure with:

Back 31

A) (5')CACTAGTTCG(3').
B) (5')CACUAGUUCG(3').
C) (5')CACUTTCGCCC(3').
D) (5')GCTTGATCAC(3').
E) (5')GCCTAGTTUG(3').

Front 32

In comparison with DNA-DNA double helices, the stability of DNA-RNA and RNA-RNA helices is:

Back 32

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.

Front 33

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):

Back 33

A) heat.
B) low pH.
C) oxygen.
D) UV light.
E) both C and D.

Front 34

Compounds that generate nitrous acid (such as nitrites, nitrates, and nitrosamines) change DNA molecules by:

Back 34

A) breakage of phosphodiester bonds.
B) deamination of bases.
C) depurination.
D) formation of thymine dimers.
E) transformation of A --> T.

Front 35

In DNA sequencing by the Sanger (dideoxy) method:

Back 35

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.