Exam 3

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Genetics Essentials
Chapters 8-11
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1

When a DNA molecule is described as replicating bidirectionally, that means that it has two:

replication forks.

2

An Okazaki fragment is a:

segment of DNA that is an intermediate in the synthesis of the lagging strand.

3

Which one of the following statements about enzymes that interact with DNA is true?

Exonucleases degrade DNA at a free end.

4

E. coli DNA polymerase III:

is the principal DNA polymerase in chromosomal DNA replication.

5

The proofreading function of DNA polymerase involves all of the following except:

reversal of the polymerization reaction.

6

The 5' → 3' exonuclease activity of E. coli DNA polymerase I is involved in:

removal of RNA primers by nick translation

7

Prokaryotic DNA polymerase III:

has a β subunit that acts as a circular clamp to improve the processivity of DNA synthesis.

8

At replication forks in E. coli:

RNA primers are synthesized by primase

9

Which of these enzymes is not directly involved in methyl-directed mismatch repair in E. coli?

DNA glycosylase

10

The role of the Dam methylase is to:

modify the template strand for recognition by repair systems.

11

The functional unit of genetic information is called:

a gene

12

The process whereby RNA specifies a DNA sequence is known as:

reverse transcription

13

Proteins interact predominantly within which portion of a double-stranded DNA helix?

major groove

14

AT-rich DNA will denature/melt

at a lower temperature than GC-rich DNA.

15

In Bacteria and most Archaea, the enzyme that introduces negative supercoils into DNA is known as

DNA gyrase

16

Ciprofloxacin, nalidixic acid, and novobiocin are effective antiobiotics because they inhibit the activity of

DNA gyrase

17

Most plasmids are

double-stranded DNA, though a few are not.

18

Housekeeping genes are present in

chromosome

19

The precursor of each new nucleotide in a strand of DNA is a

deoxynucleoside 5'-triphosphate

20

DNA replication always proceeds from the ____ of the incoming nucelotide to the _____ of the previously added molecule

5' phosphate/ 3' hydroxyl

21

During DNA synthesis, the RNA primer is removed by a

Pol I exonuclease

22

The template for RNA polymerase is _____, and the RNA chain growth is _____ the chain growth of DNA.

DNA/ Identical to

23

Promoters are specific sequences of _____ that are recognized by ______.

DNA/ sigma factor

24

An example of nucleotide pairing is

A and T

25

Stop codons are also called ____ codons.

nonsense and termination

26

There are about ____ different tRNAs in bacterial cells and about _____ in mammalian cells

60/100-110

27

tRNA is released from the ribosome at the _____ site

E

28

Which statement is generally TRUE regarding protein synthesis?

the 23S rRNA plays a role in TRANSLOCATION; the 16S rRNA plays a role in INITIATION

29

Streptomycin inhibits _____ of protein synthesis, whereas tetracycline inhibits _____ of protein synthesis

initiation/elongation

30

In all cells, genes are composed of

nucleic acids

31

Which of the following is an example of one codon?

CAG

32

Which of the following is NOT correct regarding DNA and RNA synthesis?

Both processes require an RNA primer to begin.

33

Termination of RNA synthesis is ultimately determined by

specific nucelotide sequences on the template strand.

34

GTP provides energy for

translation 

35

Transcription of chaperonins is greatly accelerated when a cell is stressed by

excessive heat

36

The flow of biological information begins with

DNA

37

Most of the genes that encode proteins are found in

unique-sequence DNA

38

Why was the discovery of the structure of DNA so important for understanding genetics?

Without knowledge of the structure of DNA, it was impossible to understand how genetic information was encoded or expressed.

39

If Avery, MacLeod, and McCarty had found that samples of heat-killed bacteria treated with rNase and DNase transformed bacteria, but that samples treated with protease did not, what conclusion would they have made?

protein is the genetic material

40

Could Hershey and Chase have used a radioactive isotope of carbon instead of 32p? Why or why not?

No: carbon is found in both protein and nucleic acid.

41

How do the sugars of rNA and DNA differ?

the sugar of rNA has a hydroxyl group that is not found in the
sugar of DNA

42

the antiparallel nature of DNA refers to

the opposite direction of the two strands of nucleotides.

43

How does Z-DNA differ from B-DNA?

Z-DNA has a left-handed helix; B-DNA has a right-handed helix. The sugar–phosphate backboneof Z-DNA zigzags back and forth, whereas the sugar– phosphate backbone of B-DNA forms a smooth continuous ribbon

44

A DNA molecule 300 bp long has 20 complete rotations. this DNA molecule is

negatively supercoiled

45

How does bacterial DNA differ from eukaryotic DNA?

Bacterial DNA is not complexed with histone proteins and is circular

46

Neutralizing their positive charges would have which effect on the histone proteins?

they would bind less tightly to the DNA

47

Which of the following is a characteristic of DNA sequences at the telomeres? a. One strand consists of guanine and adenine or thymine
nucleotides. b. they consist of repeated sequences. c. One strand protrudes beyond the other, creating some
single-stranded DNA at the end. d. All of the above

d. All of the above

48

how many bands of DNa would be expected in Meselson and Stahl’s experiment after two rounds of conservative replication?

Two bands

49

Discontinuous replication is a result of which property of DNa

antiparallel nucleotide strand

50

Place the following components in the order in which they are first used in the course of replication: helicase, single-strand-binding protein, DNa gyrase, initiator proteins.

Initiator proteins, helicase, single-strand-binding protein, DNA gyrase

51

Primers are synthesized where on the lagging strand?

At the beginning of every Okazaki fragment

52

Which bacterial enzyme removes the primers

DNA polymerase I

53

Initiator proteins

Bind to origin and separate strands of DNa to initiate replication

54

DNa helicase

Unwinds DNa at replication fork

55

Single-strand-binding proteins

attach to single-stranded DNa and prevent secondary structures from forming

56

DNa gyrase

Moves ahead of the replication fork, making and resealing breaks in the double-stranded helical DNa to release the torque that builds up as a result of unwinding at the replication fork

57

DNa primase

Synthesizes a short rNa primer to provide a 3'-Oh group for the attachment of DNa nucleotides

58

DNa polymerase III

elongates a new nucleotide strand from the 3'-Oh group provided by the primer

59

DNa polymerase I

removes rNa primers and replaces them with DNa

60

DNa ligase

joins Okazaki fragments by sealing breaks in the sugar– phosphate backbone of newly synthesized DNa

61

What are some differences from prokaryotes in the genome structure of eukaryotic cells that affect how replication takes place?

The size of eukaryotic genomes, the linear structure of eukaryotic chromosomes, and the association of DNA with histone proteins

62

What would be the result if an organism’s telomerase were mutated and nonfunctional?

Chromosomes would shorten each generation.

63

Why is recombination important?

Recombination is important for generating genetic variation.

64

Stem Loop structures are a critical part of

Rho- dependent termination and rho-independent termination

65

The main purpose of recombination is

To align truly homologous chromosomes

66

The function of gyrase is

To relieve torsional stress from unwinding DNA

67

The molar ratio of Histone H1 to H2 in the core is

1:2

68

If a splice site were mutated so that splicing did not take place, what would the effect be on the mrNA?

It would be longer than normal.

69

What evidence indicated that eukaryotic genes are not colinear with their proteins?

When DNA was hybridized to the mRNA transcribed from it, regions of DNA that did not correspond to RNA looped out

70

What is the function of the sigma factor?

The sigma factor controls the binding of RNA polymerase to the promoter.

71

What is the difference between the template strand and the nontemplate strand?

The template strand is the DNA strand that is transcribed into an RNA molecule, whereas the nontemplate strand is not transcribed.

72

Which class of rNA is correctly paired with its function?

transfer rNA (trNA): attaches to an amino acid

73

In a polyribosome, the polypeptides associated with which ribosomes will be the longest?

those at the 3' end of mrNA

74

In elongation, the creation of peptide bonds between amino acids is catalyzed by

rRNA

75

In elongation, the creation of peptide bonds between amino acids is catalyzed by

The Shine–Dalgarno sequence

76

Amino acids bind to which part of the trNA

3' end

77

through wobble, a single __________ can pair with more than one _____________.

anticodon, codon

78

A codon is

three nucleotides that encode an amino acid

79

What determines the secondary and tertiary structures of a protein?

The amino acid sequence(primarystructure) of the protein

80

Which one of the following statements is not true for all E. coli DNA polymerases?

They possess 5'to 3' exonuclease activity.

81

Which statement is true regarding negative supercoiled DNA ?

Negative supercoiled DNA is under-rotated and allows for easier strand separation during replication and transcription

82

What would Avery, Macleod, and McCarty have concluded if their results had been that only RNAse treatment of the heat-killed bacteria prevented transformation of genetic virulence?

RNA is the genetic material

83

Okazaki fragments are found associated with

Lagging strand

84

After the first round of replication, Meselson and Stahl saw only one DNA band of density intermediate to DNA containing only 15N or 14N. After this observation, which hypothesis for DNA replication could be eliminated ?

conservative

85

DNA synthesis in eukaryotes is?

semi-conservative

86

According to Chargaff’s rules, if a genome is 30% adenine, then what percentage of the genome should be guanine?

20%

87

How many base pairs per turn on DNA

10

88

What is the function of DNA Polymerase I in E.coli

Removes and replaces primers

89

What is the function of DNA Polymerase III in E.coli

Elongates DNA

90

What is the function of DNA Polymerase II, IV, and V in E.coli

DNA repair for all, ttranslesion DNA synthesis for V, II Halts synthesis, IV just repairs

91

Binds to origin and separates strand of DNA to initiate replication

Initiator protein

92

Unwinds DNA at replication fork

DNA Helicase

93

Attach to single-stranded DNA and prevent reannealing

Single-strand-binding proteins

94

Moves ahead of the replication fork, making and resealing breaks in the double-helical DNA to release torque that builds up as a result of unwinding at the replication fork

DNA gyrase

95

Synthesizes short RNA primers to provide a 3-OH group for attachment of DNA nucleotides.

DNA primase

96

Elongates a new nucleotide strand from the 3-0H group provided by the primer

DNA polymerase III

97

Removes RNA primers and replaces them with DNA

DNA Polymerase I

98

Joins Okazaki fragments by sealing nicks in the sugarophoshate backbone of newly synthesized DNA

DNA ligase

99

After crossing over results in recombination and non-recombination products take place after what?

DNA sytnthesis

100

How does Holiday junction predict crossover of recombinant DNA?

Ir depends if it was cut horizontal or vertical

101

Correct order of the Central Dogma

information from DNA--- transcription to RNA translated to protein

102

Transcribed in both eukaryotic and prokaryotic cells.

Messenger RNA (mRNA), Ribosomal RNA (rRNA), Transfer RNA (trna)

103

Transcribed in only eukaryotic celss

Pre-messenger RNA (pre-mRNA), Small nuclear RNA (snRNA), Small nucleolar RNA (snoRNA), MicoRNA(miRNA), small interfering RNA (siRNA)

104

Structural and functional components of the ribosome

rRNA

105

Carries genetic code for proteins

mRNA

106

helps incorporate amino acids into polypeptide chain

tRNA

107

Processing of pre-mRNA

snRNA

108

processing and assembly of rRNA

snoRNA

109

Inhibits the translation of mRNA

MiRNA

110

Triggers the degradation of other RNA Molecules

siRNA

111

In translated RNA what sequence is only found in prokaryotes

Shine-Delgarno sequence

112

In translated RNA what sequence is only found in eurakryotes

Kozak Sequence

113

in excision of transcripts 5 prime is

the branch point

114

in excision of transcripts 3 prime is

The consensus sequence

115

u1 in a spliceosome

is snrna

116

Purines are what base nucleotides

A and G

117

pyridines are what base nucleotides

T and C

118

In mRNA 5' to 3' goes from what chemical group to the other.

Amino to Carboxyl

119

Basic order of charged TRNA

First Aminoacyl second Peptidyl and E exit.