Deck 19: Nucleic Acids

Question 1

The abbreviation pdAp indicates

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

Answer 1

5ʹ, 3ʹ deoxyadenylate.

Question 2

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

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

Answer 2

3ʹ-5ʹphosphodiester bonds.

Question 3

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.

Answer 3

C.

Question 4

Cells fed5-methyl uracil radioactive in the methy group) will form radioactive .

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

Question 5

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 6

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 7

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 8

Adenylate and AMP each contain phosphate groups.

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

Question 9

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 10

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 11

Deoxythymidine is a found mainly in DNA.

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

Question 12

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 13

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 1 mm in length?

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

Question 14

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 15

The abbreviation dGp indicates

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

Question 16

The abbreviation pppT indicates

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

Question 17

ʺFive prime to three primeʺ description of a DNA strand refers to

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

Question 18

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.
C) the helix pitch is longer in AT rich regions.
D) All of the above

Question 19

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

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

Question 20

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 21

Which does not apply to most bacterial DNA?

A) circular
B) relaxed
C) not packed into nucleosomes
D) supercoiled

Question 22

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 23

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 24

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 25

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 26

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

A) ribosomal
B) messenger
C) small
D) transfer

Question 27

What is the function of DNA toposiomerases?

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 28

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 29

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 single-stranded; DNA is double-stranded.

Question 30

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 31

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 32

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 33

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 34

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

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

Question 35

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

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

Question 36

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

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

Question 37

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 38

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 39

Chromatin was first observed and named by .

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

Question 40

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

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

Question 41

Which recognition sequence is not a palindrome? DNA sequences are shown in the standard 5ʹ →3ʹ 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 42

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 43

The 30 nm fibers of a chromosome are attached to a/an scaffold that holds the fibers in large loops.

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

Question 44

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

Question 45

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 46

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 47

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 48

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 49

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 speciesʹ 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 50

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 51

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 52

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 2ʹ-hydroxyl group by histidine.
D) Transition-state stabilization of a pentavalent phosphorous atom.

Question 53

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 54

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 55

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 56

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 57

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 58

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

Question 59

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

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

Question 60

All genomes are composed of RNA.

Question 61

Messenger RNA is the least stable type of cellular ribonucleic acid.

Question 62

RNA does not have a double strand form.

Question 63

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

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

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

Question 66

RNAs are single-stranded molecules with little complex secondary structure.

Question 67

Prokaryotic DNA is organized into protein-DNA structures called nucleoids.

Question 68

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

Question 69

For double-stranded DNA ending in an AT pair, both A and T will have a phosphate at the 5ʹ position.

Question 70

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

Question 71

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

Question 72

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

Question 73

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

Question 74

Topoisomerases cut one or both coiled DNA strands, wind the ends by rotation, and then rejoin the cut ends.

Question 75

Strands in the stem of stem-loop RNA structures are parallel.

Question 76

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

Question 77

About 150 bp of DNA wrap around the histone octamer to form a bead-like structure. The
ʺbeadsʺ are separated by about 50 bp of linker DNA.

Question 78

The supercoiling of double-stranded circular DNA can be removed by cleaving a single phosphodiester bond on only one strand nicking).

Question 79

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

Question 80

It is not possible for linear DNA to be supercoiled. Only circular DNA, which has no ends, can have regions of supercoiling.