Test 3

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1

Introns are significant to biological evolution because
a. they correct enzymatic alterations of DNA bases
b. their presence allows exons to be shuffled
c. they are translated into essential amino acids
d. they protect the mRNA from degeneration
e. they maintain the genetic code by preventing incorrect DNA base pairings

b.

2

Why are viruses referred to as obligate parasites?
a. they must use enzymes encoded by the virus itself
b. they can incorporate nucleic acids from other viruses
c. they invariably kill any cell they infect
d. they cannot reproduce outside of a host cell
e. viral dan always inserts itself into host DNA

d.

3

What is the function of reverse transcriptase in retroviruses?
a. it uses viral DNA as a template for making complementary RNA strands
b. it hydrolyzes the host cells DNA
c. it translates viral RNA into proteins
d. it converts host cell RNA into viral DNA
e. it uses viral DNA as a template for DNA synthesis

e.

4

Which of the following help(s) to stabilize mRNA by inhibiting its degradation?
a. spliceosomes
b. introns
c. TATA box
d. 5' cap and poly A tail
e. RNA polymerase

d.

5

Most molecular biologists think that viruses originated from fragments of cellular nucleic acids. Which of the following observations supports this theory?
a. viruses are enclosed in protein capsids rather than plasma membranes
b. viruses can reproduce only inside host cells
c. viruses contain either DNA or RNA
d. viruses can infect both prokaryotic and eukaryotic cells
e. viral genomes are usually more similar to the genome of the host cell than to the genomes of virues that infect other cell types

e.

6

Which of the following describes the function of an enzyme known as Dicer?
a. it degrades single stranded mRNA
b. it trims small double stranded RNAs into molecules that can block translation
c. it degrades mRNA with no poly A tail
d. it chops up single stranded DNAs from interfering viruses
e. it degrades single stranded DNA

b.

7

In which of the following actions foes RNA polymerase differ from DNA polymerase?
a. RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis
b. RNA polymerase uses RNA as a template, and DNA polymerase uses a DNA template
c. RNA polymerase is much more accurate than DNA polymerase
d. RNA polymerase does not need to separate the two strands of DNA in order to synthesize

a.

8

Which of the following removes the RNA nucleotides from the primer and adds equivalent RNA nucleotides to the 3' end of Okazaki fragments?
a. primase
b. ligase
c. helicase
d. DNA polymerase l
e. DNA polymerase lll

d.

9

Which of the following is the most probable fate of a newly emerging virus that causes high mortality in its host?
a. the newly emerging virus will die out rather quickly or will mutate to be far less lethal
b. a change in environmental conditions such as weather patterns quickly forces the new virus to invade new areas
c. the new virus replicates quickly and undergoes rapid adaptation to a series of divergent hosts
d. sporadic outbreaks will be followed almost immediately by a widespread pandemic
e. its able to spread to a large number of new hosts quickly because the new hosts have no immunological memoiry of them

a.

10

what are the coding segments of a stretch of eukaryotic DNA called?
a. exons
b. introns
c. replicons
d. transposons
e. codons

a.

11

Genomic imprinting, DNA methylation, and histone acetylation are all examples of
a. translocation
b. genetic mutation
c. karyotypes
d. epigenetic phenomena
e. chromosomal rearragements

d.

12

This binds to a site in the DNA far from the promoter to stimulate transcription
a. repressor
b. enhancer
c. terminator
d. promoter
e. activator

e.

13

In his transformation experiments, what did Griffith observe?
a. mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form
b. infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains
c. mutant mice were resistant to bacterial infections
d. mixing a heat killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic
e. mice infected

a.

14

Once transcribed, eukaryotic mRNA typically undergoes substantial alteration that includes
a. fusion with other newly transcribed mRNA
b. excision of introns
c. fusion into circular forms known as plasmids
d. union with ribosomes
e. linkage to histone molecules

b.

15

The phenomenon i which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double stranded RNA is called
a. RNA disposal
b. RNA obstruction
c. RNA blocking
d. RNA targeting
e. RNA interference

e.

16

Which of the following accounts for someone who has had a herpesvirus-mediated cold sore or genital sore getting flare ups for the rest of their life?
a. co-infection with an unrelated virus that causes the same symptoms
b. re-infection by the same herpesvirus strains
c. re-infection by a closely related herpesvirus of a different strain
d. copies of the herpesvirus genome permanently maintained in the host cell cytoplasm
e. copies of the herpesvirus genome permanently maintained in host nuclei

e.

17

Which of the following separates the DNA strands during replication?
a. DNA polymerase lll
b. DNA polymerase l
c. primase
d. helicase
e. ligase

d.

18

RNA polymerase moves in which direction along the DNA?
a. 3'->5' along the coding strand
b. 5'->3' along the template strand
c. 3'->5' along the coding (sense) strand
d. 5'->3' along the double stranded DNA
e. 3'->5' along the template strand

e.

19

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?
a. join Okazaki fragments together
b. synthesize RNA nucleotides to make a primer
c. stabilize the unwound parental DNA
d. unwind the parental double helix
e. catalyze the lengthening of telomeres

a.

20

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?
a. DNA contains purines, whereas protein includes pyrimidines
b. DNA contains phosphorus, but protein does not
c. DNA contains nitrogen, whereas protein does not
d. DNA contains sulfur, protein does not
e. DNA includes ribose, while DNA includes deoxyribose sugars

b.

21

What is a ribozyme?
a. an enzyme that synthesizes RNA as part of the transcription process
b. an enzyme that synthesizes RNA primers during DNA replication
c. an enzyme that uses RNA as a substrate
d. an enzyme that catalyzes the association between the large and small ribosomal units
e. an RNA with enzymatic activity

e.

22

Why do RNA viruses appear to have higher rates of mutation?
a. RNA viruses can incorporate a variety of nonstandard bases
b. RNA viruses are more sensitive to mutagens
c. RNA nucleotides are more unstable than DNA nucleotides
d. RNA viruses replicate faster
e. Replication of their genomes does not involve the proofreading steps of DNA replication

e.

23

This can inhibit transcription by blocking the binding of positively acting transcription factors
a. enhancer
b. promoter
c. activator
d. terminator
e. repressor

e.

24

As a ribosome translocates along an mRNA molecule by one codon, which of the following occurs?
a. The polypeptide enters the E site
b. the tRNA that was in the A site moves to the E site and is released
c. the tRNA that was in the P site moves into the A site
d. the tRNA that was in the A site moves into the P site
e. the tRNA that was in the A site departs from the ribosome via a tunnel

d.

25

What is the name given to viruses that are single-stranded RNA that acts as a template for DNA synthesis?
a. retroviruses
b. proviruses
c. viroids
d. bacteriophages
e. lytic phages

a.

26

Which of the following synthesizes short segments of RNA?
a. ligase
b. DNA polymerase l
c. DNA polymerase lll
d. helicase
e. primase

e.

27

A part of the promoter called the TATA box is said to be highly conserved in evolution. Which might this illustrate?
a. the sequence is found in many but not all promoters
b. any mutation in the sequence is selected against
c. the sequence does not mutate
d. the sequence is transcribed at the start of every gene
e. the sequence evolves very rapidly

b.

28

How does active CAP induce expression of the genes at the lactose operon?
a. it stimulates splicing of the encoded genes
b. it stimulates the binding of RNA polymerase to the promoter
c. it binds steroid hormones and controls translation
d. it degrades the substrate allolactose
e. it terminates production of repressor molecules

b.

29

Which of the following investigators was/were responsible for the following discovery?
Chemicals from heat-killed S cells were purified. The chemicals were tested for the ability to transform live R cells. The transforming agent was found to be DNA.
a. Erwin Chargaff
b. Frederick Griffith
c. Oswald Avery, Maclyn McCarty, and Colin MacLeod
d. Alfred Hershey and Martha Chase
e. Matthew Meselson and Franklin Stahl

c.

30

A lack of this nonprotein molecule would result in the inability of the cell to "turn off" genes
a. operon
b, inducer
c. promoter
d. corepressor
e. repressor

d.

31

What determines the nucleotide sequence of the newly synthesized strand during RNA replication?
a. the primes used in the reaction
b. the nucleotide sequence of the template strand
c. the particular DNA polymerase catalyzing the reaction
d. the arrangement of histones in the sugar phosphate backbone
e. the relative amounts of the four nucleotides triphosphates in the cell

b.

32

Choose the answer that has these events of protein synthesis in the proper sequence
1. An aminoacyl-tRNA binds to the A site
2. A peptide bond forms between the new amino acid and a polypeptide chain
3. tRNA leaves the P site, and the P site remains vacant
4. A small ribosomal subunit binds with mRNA
5. tRNA translocates to the P site
a. 4,1,2,3,5
b. 2,4,5,1,3
c. 5,4,3,2,1
d. 1,3,2,4,5
e. 4,1,3,2,5

a.

33

When this is taken up by the cell, it binds to the repressor so that the repressor no longer binds to the operator
a. repressor
b. promoter
c. inducer
d. operon
e. corepressor

c.

34

Why does the DNA double helix have a uniform diameter?
a. C nucleotides pair with A nucleotides
b. Nucleotides bind with nucleoside triphosphates
c. Nucleotides bind with nucleosides
d. Purines pair with pyrimidines
e. Deoxyribose sugars bind with ribose sugars

d.

35

Which of the following statements describes the lysogenic cycle of lambda phage?
a. certain environmental triggers can cause the phage to exit the host genome, switching from the lytic to the lysogenic
b. most of the prophage genes are activated by the product of a particular prophage gene
c. the phage DNA is incorporated by crossing over into any nonspecific site on the host cells DNA
d. The phage genome replicates along with the host genome
e. After infection, the viral genes immediately turn the host cell into a lambda-producing factory, and the host cell then lyses

d.

36

The host range of a virus is determined by
a. whether its nucleic acid is DNA or RNA
b. the proteins on its surface and that of the host
c. the enzymes produced by the virus before it infects the cell
d. the proteins in the host's cytoplasm
e. the enzymes carried by the virus

b.

37

Alternative RNA splicing
a. is due to the presence or absence of particular snRNPs
b. is a mechanism for increasing the rate of transcription
c. can allow the production of proteins of different sizes from a single mRNA
d. can allow the production of similar proteins from different RNAs
e. increases the rate of transcription

c.

38

Altering patterns of gene expression in prokaryotes would most likely serve the organism's survival in which of the following ways?
a. allowing environmental changes to alter the prokaryote's genome
b. allowing young organisms to respond differently from more mature organisms
c. allowing the organism to adjust to changes in environmental conditions
d. allowing each gene to be expressed an equal number of times
e. organizing gene expression so that genes are expressed in a given order

c.

39

What kind of chemical bond is found between paired bases of the DNA double helix?
a. hydrogen
b. ionic
c. covalent
d. phosphate
e. sulfhydryl

a.

40

The tryptophan operon is a repressible operon that is
a. turned on only when tryptophan is present in the growth medium
b. turned off whenever tryptophan is added to the growth medium
c. turned off only when glucose is present in the growth medium
d. turned on only when glucose is present in the growth medium
e. permanently turned on

b.

41

Replication in prokaryotes differs from replication in eukaryotes for which of these reasons?
a. prokaryotes have telomeres, and eukaryotes do not
b. the rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes
c. prokaryotes produce okazaki fragments during DNA replication, but eukaryotes do not
d. prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many
e. the prokaryotic chromosome has histones, whereas eukaryotic chromosomes do not

d.

42

The DNA of telomeres has been found to be highly conserved throughout the evolution of eukaryotes. What does this most prob reflect?
a. the inactivity of this DNA
b. that the critical function of telomeres must be maintained
c. that new evolution of telomeres continues
d. that mutations in telomeres are relatively advantageous
e. the low frequency of mutations occurring in the DNA

b.

43

This is the site in the DNA located near the end of the final exon, encoding an RNA sequence that determines the 3' end of the transcript
a. activator
b. repressor
c. terminator
d. enhancer
e. promoter

c.

44

What does the operon model attempt to explain?
a. how genes move between homologous regions of DNA
b. the coordinated control of gene expression in bacteria
c. the mechanism of viral attachment to a host cell
d. bacterial resistance to antibiotics
e. horizontal transmission of plant viruses

b.

45

What are prions?
a. viruses that invade bacteria
b. misfolded versions of normal brain protein
c. tiny molecules of RNA that infects plants
d. viral DNA that has had to attach itself to the host genome
e. a mobile segment of DNA

b.


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