Deck 19: Nucleic Acids

Question 1

The abbreviation pdAp indicates

A)5',3' deoxyadenylate.
B)3',5' deoxyadenylate.
C)5' deoxyadenylate.
D)3' deoxyadenylate.
E)None of the above.

Answer 1

5',3' deoxyadenylate.

Question 2

The abbreviation dGp indicates

A)5' deoxyguanylate.
B)3' deoxyguanylate.
C)3',5' deoxyguanylate.
D)5',3'deoxyguanylate.
E)None of the above.

Answer 2

3' deoxyguanylate.

Question 3

Cells fed 5-methyl uracil (radioactive in the methyl group)will form radioactive ________.

A)RNA
B)DNA
C)ribosomes
D)tRNA
E)A,C and D

Answer 3

DNA

Question 4

ATP is not a nucleoside because it ________.

A)has phosphate groups
B)has three phosphates instead of just one
C)lacks the deoxyribosyl group
D)is not connect to a carbohydrate group

Question 5

Adenylate and AMP each contain ________ phosphate group(s).

A)0
B)1
C)2
D)3
E)None of the above

Question 6

The abbreviation pppT indicates

A)TMP.
B)TDP.
C)TTP.
D)3,5' TP.
E)None of the above.

Question 7

Which of the following is mismatched?

A)Miescher - discovery of DNA.
B)Avery - DNA is the genetic material.
C)Watson - DNA structure.
D)Hoppe-Seyler - DNA sequence.

Question 8

How might mitochondrial DNA be distinguished from eukaryotic nuclear DNA?

A)Mitochondrial DNA is in the Z conformation,nuclear DNA is in the B conformation.
B)Mitochondrial DNA is methylated,nuclear DNA is not.
C)Nuclear DNA is linear,mitochondrial DNA are circular.
D)They cannot be distinguished and must be clearly separate during purifcation.

Question 9

Approximately how many base pairs are there in a B-DNA segment with 50 helical turns?

A)5
B)50
C)500
D)5000

Question 10

What is the approximate diameter of a DNA molecule?

A)A few picometers.
B)A few Angstroms.
C)A few nanometers.
D)A few micrometers.

Question 11

Much of the stability of the double-stranded DNA structure is the result of

A)hydrogen bonding between purines.
B)the phosphodiester backbone.
C)the angle of the planes of the bases with respect to the helix axis.
D)the stacking interactions between base pair.

Question 12

According to Chargaff's observations of nucleotide composition of DNA samples

A)% of (G + C)+ % of (A + T)= 100%.
B)A = T.
C)G = C.
D)%A + %G + %C + %T = 100%.
E)All of the above.

Question 13

Deoxythymidine is a ________ found mainly in DNA.

A)nucleotide
B)deoxynucleotide
C)nucleoside
D)deoxynucleoside
E)glycoside

Question 14

The difference between dGMP and GMP is

A)the type of phosphodiester linkage.
B)one hydroxyl group.
C)syn versus anti conformation.
D)the presence of DNA or RNA.

Question 15

Regions of DNA that are most easily unwound have

A)about half G and half C.
B)alternating A and G.
C)greater G:C content.
D)greater A:T content.

Question 16

The rise and pitch of B-DNA are 0.33 nm and 3.40 nm,respectively.About how many helical turns are there in a fragment 1000 nm in length?

A)3030
B)294
C)330
D)0.0034
E)Cannot calculate from the information given.

Question 17

Purines which are found mainly in both deoxyribonucleotides and ribonucleotides are

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

Question 18

Protein X recognizes and binds to a particular (normal and undamaged)DNA sequence.Which statement applies?

A)The protein can recognize the sequence by accessing the bases at the major or minor groove.
B)The protein can recognize sequence-dependent differences in the distance between the sugar-phosphate backbones of the two strands.
C)The protein must have a cofactor to separate the DNA strands to access and recognize the sequence.
D)The protein must be dimeric to recognize the complementary sequences on each strand.

Question 19

Purines and pyrimidines exist in two tautomeric forms (lactam and lactim);nucleosides exist in two conformations (syn and anti).The most common forms found in cells are

A)lactam and anti.
B)lactam and syn.
C)lactim and anti.
D)lactim and syn.

Question 20

In DNA,phosphodiester bonds form with hydroxyl groups of carbons number ________ and ________ of each deoxyribose sugar.

A)2';3'
B)2';4'
C)3';4'
D)3';5'
E)4';5'

Question 21

Which type of RNA carries activated amino acids to the ribosome for assembly into proteins?

A)rRNA.
B)tRNA.
C)mRNA.
D)sRNA.

Question 22

In addition to knowing the chemical structures of the nucleotides,Watson and Crick used ________ of Franklin and Wilkins and the chemical equivalencies of Chargaff in order to propose their model of DNA structure.

A)sequence information
B)UV spectra
C)% (G +C)and % (A +T)
D)X-ray diffraction data

Question 23

What is the function of DNA topoisomerases?

A)Cleaving nucleotides from the ends of DNA.
B)Adding or removing supercoils.
C)Methylation of the nitrogenous bases.
D)Packaging of DNA into nucleosomes.

Question 24

"Five prime to three prime" description of a DNA strand refers to

A)the phosphorylated 5' carbon at one end,the 3' at the other end.
B)the location of the hydroxyl groups.
C)the phosphodiester backbone of DNA.
D)the phosphorylated 5' carbon on one sugar and the 3' carbon on the next sugar.

Question 25

Which is not true of the different conformations of DNA?

A)Z-DNA is a left-handed spiral.
B)A-DNA and B-DNA are right-handed spirals.
C)A-DNA and Z-DNA segments are limited to short regions of DNA.
D)Both A-DNA and B-DNA are dehydrated.

Question 26

Which is not a difference between RNA and DNA?

A)The sugar ring of RNA is more oxidized than that in DNA.
B)RNA contains uracil;DNA usually does not.
C)RNA cannot form helices.
D)RNA is usually single-stranded;DNA is double-stranded.

Question 27

Stem-loop is a type of secondary structure not usually found in

A)rRNA.
B)tRNA.
C)mRNA.
D)small RNA.

Question 28

________ plays an important role in storing the energy needed for the unwinding of DNA during replication,recombination,repair and transcription.

A)A high percent of G:C base pairs
B)The charge on basic side chains of histone proteins
C)Negative supercoiling
D)Overwinding of the helix

Question 29

The tetranucleotide AGTC (in DNA)has a free hydroxyl group on

A)A.
B)A,G,T,and C.
C)C.
D)G,T,and C.

Question 30

In proteins,amino acids are linked by peptide bonds;in polynucleotides,nucleotides are linked by

A)phosphoanhydride bonds.
B)3'-5'phosphodiester bonds.
C)5'-3'phosphodiester bonds.
D)B and C.
E)All of the above.

Question 31

Which type of RNA is the most abundant in living cells (by percent)?

A)Ribosomal.
B)Messenger.
C)Small.
D)Transfer.

Question 32

As B-DNA is gradually heated,the absorbance at 260 nm

A)increases.
B)decreases.
C)stays the same.
D)is half way between that of poly (AT and poly (GC).

Question 33

Supercoiling of pure circular DNA is a result of ________.

A)underwinding or overwinding of the helix
B)entanglements because of the long length of the strands
C)the lack of associated histones
D)the activity of exonucleases

Question 34

Which of the following is mismatched?

A)B-DNA: dehydrated.
B)Z-DNA: left-handed helix.
C)A-DNA: dehydrated.
D)Z-DNA: no major or minor grooves.
E)B-DNA: right-handed helix.

Question 35

Which is not a difference between B-DNA and A-DNA?

A)A-DNA forms under more dehydrating conditions than B-DNA.
B)For polynucleotide strands containing the same number of nucleotides,the A-DNA strand will be shorter from end-to-end than the corresponding B-DNA.
C)Both are helical,but B-DNA is right-handed and A-DNA is left-handed.
D)The planes of the nitrogenous bases are not perpendicular to the helix axis in A-DNA.

Question 36

Changes in the topology and three-dimensional shape of B-DNA can result from

A)incubation with proteases.
B)supercoiling.
C)isomerization.
D)hydration.

Question 37

For DNA,a plot of the change in absorbance versus temperature would be ________,which indicates ________.

A)hyperbolic;a simple equilibrium between the native conformation and denatured DNA
B)linear;the breaking of bonds between the base pairs is an independent process
C)variable in shape (hyperbolic,linear or sigmoidal);the dependence of the denaturing process on the sequence of the DNA
D)sigmoidal;cooperativity where disruptions in the base stacking at one position destabilizes the stacking in neighboring base pairs

Question 38

Which does not apply to most bacterial DNA?

A)Circular.
B)Relaxed.
C)Not packed into nucleosomes.
D)Supercoiled.

Question 39

Which of the following is mismatched?

A)rRNA: 80% of cellular RNA.
B)tRNA: carry amino acids during protein synthesis.
C)mRNA: stable RNA carrying the coded information from DNA.
D)Small RNA: catalytic with or without proteins.

Question 40

It is easier to melt DNA richer in AT than GC because

A)it is more heat sensitive.
B)there is one less hydrogen bond in an AT base pair.
C)the helix pitch is longer in AT rich regions.
D)All of the above.

Question 41

Which is not a biological function of RNA?

A)Participates in the modification of newly synthesized RNA.
B)It is the genome of some viruses.
C)Serves as a scaffold component for chromosomes.
D)Composes an integral part of the ribosome.
E)None of the above;all are functions of RNA.

Question 42

Which are the products of the RNase A-catalyzed hydrolysis of pGpApUpApApCpG?

A)pG + pA + pUpA + pA + pCpG
B)pGpApU + pApApC + pG
C)pG + pApUpApApCpG
D)pGpApUp + ApApCp + G
E)two pG + three pA + pU + pC

Question 43

Histones associate with DNA primarily through ________.

A)hydrogen bonding
B)hydrophobic interactions with the exposed bases in the major groove
C)ionic interactions with the phosphate groups
D)disulfide linkages

Question 44

All five histones are rich in ________ amino acid residues whose positive charges allow binding to the sugar-phosphate backbone of DNA.

A)lysine and alanine
B)lysine and arginine
C)leucine and alanine
D)leucine and arginine

Question 45

Chromatin was first observed and named by ________.

A)Walter Flemming
B)Francis Crick
C)Oswald Avery
D)Friedrich Miescher

Question 46

Which best describes the structure of a nucleosome core particle?

A)A histone octamer with DNA threaded through its center.
B)About 50 bp of DNA associated with one histone H1 molecule.
C)One nucleosome plus one histone H1 and linker DNA.
D)A histone octamer wrapped approximately two times around with DNA.

Question 47

What is the effect of incubating a mixture of RNA and DNA with 0.1 M NaOH?

A)RNA is hydrolyzed to nucleoside monophosphates.
B)DNA is hydrolyzed to nucleoside monophosphates.
C)Both RNA and DNA are hydrolyzed to nucleoside monophosphates.
D)No effect.RNA and DNA are resistant to base hydrolysis.

Question 48

What is the approximate diameter of a chromatin fiber?

A)3 nm
B)30 nm
C)300 nm
D)3 mm
E)30 mm

Question 49

DNA wraps around an octamer of histones to form bead-like structures called ________.

A)nucleoids
B)nucleosomes
C)nucleoli
D)chromatids

Question 50

About how many nucleosomes could be made from a DNA strand consisting of 1000 base pairs?

A)5
B)50
C)500
D)This is not enough DNA to make even one nucleosome.

Question 51

Histone ________ is not part of the histone octamer,but binds to linker DNA and is responsible for higher-order chromatin structure.

A)H1
B)H2
C)H3
D)H4
E)None of the above

Question 52

Which statement is not true about histones?

A)They are positively charged at biological pH.
B)They only occur in eukaryotes.
C)Most species that have histones contain five different types.
D)There is wide variation in the amino acid sequences of histones among species.

Question 53

Which recognition sequence is not a palindrome? (DNA sequences are shown in the standard 5'→3' direction)

A)GGGCCC.
B)TCTAGA.
C)AAGCTT.
D)Both B and C.
E)None of the above.All of the sequences shown are palindromes.

Question 54

The packaging of DNA in cells results in about a ________-fold reduction in length compared to the fully extended DNA (fully stretched out).

A)10
B)700
C)8000
D)200,000

Question 55

A HATS enzymes reacts with the side-chain of lysine to form the following structure: What effect will the HATS enzymes have on histones?

A)No effect,since histones contain few lysine residues.
B)HATS will increase the affinity of histones for DNA.
C)HATS will allow for easier unravelling of histone-DNA structures.
D)HATS activate histones for interaction with mRNA.

Question 56

________ catalyze the hydrolysis of phosphodiester linkages to release nucleotide residues from only one end of a polynucleotide chain.

A)Topoisomerases
B)Endonucleases
C)Exonucleases
D)Restriction enzymes

Question 57

Bacteria produce many restriction endonucleases.What prevents these enzymes from degrading the host DNA?

A)A bacterium will produce endonucleases that recognize sequences that are not present in its own DNA.
B)The strong association between the histones and bacterial DNA prevent the endonucleases from acting on them.
C)The endonucleases are transported out of the cell so quickly they cannot significantly affect the host DNA.
D)The host DNA is specifically methylated and is therefore protected from cleavage.

Question 58

The 30 nm fibers of a chromosome are attached to a(n)________ scaffold that holds the fibers in large loops.

A)RNA-protein
B)glycoprotein
C)actin filament
D)histone

Question 59

What is the order of packaging of chromatin in eukaryotic cells from smallest to largest size?

A)double-helix → solenoid → nucleosome → chromosome
B)double-helix → chromatin → solenoid → chromosome
C)single-stranded DNA → chromatin → histones → chromosome
D)double-helix → nucleosomes → solenoid → chromosome

Question 60

Stem-loop structures in RNA resemble the ________ form of double-helical DNA.

A)A
B)B
C)Z
D)supercoiled circular

Question 61

The genome of a species does not include the DNA in mitochondrial and chlorplast DNA.

Question 62

Examine the data given for a set of endonuclease digests of a 1000 bp DNA fragment.Then choose the restriction sites for Enzyme #2 on the restriction map shown.The restriction map displays all sites for both enzymes. Digestion with Enzyme #1 produces fragments of 200 bp and 400 bp.
Digestion with Enzyme #2 produces fragments of 200 bp,300 bp and 500 bp.
Simultaneous digestion with both enzymes yields fragments of 100 bp,200 bp and 300bp

A)Sites W and Y
B)Sites X,Y and Z
C)Sites X and Z
D)Sites W and X

Question 63

There are many viruses whose entire genome is Z-DNA.

Question 64

The two strands of double-stranded DNA have the same content of each of the bases A,T,G and C.

Question 65

Two DNA sequences,each 48 kb in size,are treated with the same restriction enzyme.There is only one site for this restriction enzyme on each of these sequences.Digests are separated by gel electrophoresis.Sequence A shows ONE band that is 48 kb in size.Sequence B shows TWO bands,one 30 kb and the other 18 kb in size.What can you conclude from these data?

A)They are identical sequences.
B)Both sequences are linear.
C)Sequence A is circular;sequence B is linear.
D)Sequence A is linear;sequence B is circular.

Question 66

Restriction endonucleases recognize specific DNA sequences by ________.

A)contacting base pairs in the major groove
B)inserting amino acid side chains between the base pairs and interrupting the stacking interactions
C)hydrogen bonding with base pairs in the minor groove
D)detecting base pair-depended variations in the sugar-phosphate backbone

Question 67

Five different bases are found in most DNA and RNA molecules.

Question 68

Which enzyme would be least useful for recombination experiments that introduce new fragments of DNA into an existing DNA molecule?

A)EcoRI G↓AATTC.
B)SmaI CCC↓GGG.
C)XhoI C↓TCGAG.
D)All are equally useful.

Question 69

Deoxyribonucleosides and ribonucleotides contain two hydroxyl groups that can be phosphorylated.

Question 70

It is often not possible to determine the exact sequence of large polynucleotides such as RNA and DNA.

Question 71

The recognition site of some restriction enzymes are shown.Which will produce sticky ends?

A)EcoRI G↓AATTC.
B)SmaI CCC↓GGG.
C)XhoI C↓TCGAG.
D)Both EcoRI and XhoI.
E)All the enzymes shown will leave sticky ends.

Question 72

In any species,the % (A +T)is equal to the % (G +C).

Question 73

What is a restriction map?

A)The nucleotide sequence recognized by a particular restriction enzyme.
B)Diagram of a DNA molecule to show specific cleavage sites of endonucleases.
C)Table of enzymes that have a least one site in a species' DNA.
D)A diagram of the compaction of DNA by packing into nucleosomes and solenoids.
E)A gel electrophoresis technique used for the purpose of DNA fingerprinting.

Question 74

In any species,the ratio of the % (A +T)to the % (G +C)is constant.

Question 75

It is possible to synthesize DNA containing specific polynucleotide bases today.

Question 76

Which does not occur during the hydrolysis of RNA by RNase A?

A)Covalent catalysis involving a bond between a pyrimidine and a lysine of RNase A.
B)Acid-base catalysis to cleave the phosphodiester bond.
C)Abstraction of a proton from the 2'-hydroxyl group by histidine.
D)Transition-state stabilization of a pentavalent phosphorous atom.

Question 77

The major and minor grooves are the same in B-DNA,A-DNA,and Z-DNA.

Question 78

All genomes are composed of RNA.

Question 79

Uracil is found in most RNA,while 5-methyluracil is found in most DNA.

Question 80

Absorption of single-stranded DNA at 260 nm is less than that of double-stranded DNA.