Multiple choice. Choose the one alternative that best completes the statement or answers the question



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MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

1) All of the following elements are present in DNA except

A) nitrogen.

B) phosphorus.

C) sulfur.

D) carbon.

E) oxygen.
2) If radioactive sulfur (35S) is used in a culture medium of bacteria that contains phage viruses, it will later appear in the

A) viral coats.

B) bacterial cell wall.

C) viral DNA.

D) bacterial RNA.

E) viral RNA.


3) What kind of chemical bonds are found between paired bases of the DNA double helix?

A) ionic B) sulfhydryl C) hydrogen D) phosphate E) covalent


4) All of the following statements apply to the Watson and Crick model of DNA except

A) The two strands of the DNA form a double helix.

B) The purines are attracted to pyrimidines.

C) The framework of the helix consists of sugar-phosphate units of the nucleotides.

D) The two strands of the helix are held together by covalent bonds.

E) The distance between the strands of the helix is uniform.


5) Which enzymes catalyze the elongation of a DNA strand in the 5' rightarrow 3' direction?

A) DNA polymerases

B) helicase

C) DNA ligase

D) primase

E) topoisomerase


6) In DNA, the designations 3' and 5' refer to the

A) carbon or nitrogen atoms on the rings of purine or pyrimidine bases.

B) cross-linking of the third and fifth carbon atoms of deoxyribose.

C) bonding between purines and deoxyribose and between pyrimidines and deoxyribose.

D) bonds that form between adenine and thymine and between guanine and cytosine.

E) carbon atoms of deoxyribose to which phosphate groups may bond.


7) A new DNA strand only elongates in the 5' to 3' direction because

A) DNA polymerase adds nucleotides only to the free 3' end.

B) Okazaki fragments prevent elongation in the 3' to 5' direction.

C) replication must progress toward the replication fork.

D) DNA polymerase begins adding nucleotides at the 5' end.

E) the polarity of the DNA molecule prevents addition of nucleotides at the 3' end.


8) The elongation of the leading strand during DNA synthesis

A) progresses away from the replication fork.

B) occurs in the 3' to 5' direction

C) produces Okazaki fragments

D) depends on the action of DNA polymerase

E) does not require a template strand


9) The problem of replicating the lagging strand of DNA¹that is, adding bases in the 3' rightarrow 5' direction¹requires which of the following?

A) Okazaki fragments

B) DNA ligase

C) RNA primers

D) A and B only

E) A, B, and C


10) A eukaryotic cell lacking telomerase would

A) be unable to take up DNA from the surrounding solution.

B) be unable to identify and correct mismatched mucleotides in its daughter DNA strands.

C) experience a gradual reduction of chromosome length whith each replication cycle.

D) have a greater potential to become cancerous

E) incorporate one extraneous nucleotide for each Okazaki fragment added.


11) What is the primer that is required to initiate the synthesis of a new DNA strand?

A) ligase B) DNA C) primase D) RNA E) protein


12) What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

A) catalyze the lengthening of telomeres

B) unwind the parental double helix

C) stabilize the unwound parental DNA

D) synthesize RNA nucleotides to make a primer

E) join Okazaki fragments together


13) In making a movie, sometimes an editor will cut out one piece of film and insert another. This is analogous to which of the following?

A) mismatch repair

B) transformation repair

C) excision repair

D) telomerase repair

E) recombinational repair


14) Of the following, the most reasonable inference from the observation that defects in DNA repair enzymes contribute to some forms of cancer is that

A) cancer is generally inherited

B) uncorrected changes in DNA can cause cancer

C) cancer cannot occur when DNA repair enzymes work properly

D) mutations generally lead to cancer

E) cancer is caused by environmental factors that damage DNA repair enzymes


15) With each replication of the DNA molecule, the DNA molecule becomes shorter.

A) This is due to the fact that thymine dimers cause DNA to buckle and interfere with DNA replication.

B) This is best explained by the fact that DNA polymerase can only add nucleotides to a 3' end.

C) This is not a problem because the telomere is a nonessential repeating unit.

D) This is true only if the organism has been exposed to excessive amounts of ultraviolet rays of sunlight.

E) This problem is resolved by telomerase, which extends the 3' end of the DNA.


The following questions refer to the following simple metabolic pathway
table ( ( enzyme a enzyme b ) ( A label_arrow_right_over B label_arrow_right_over C ) (~%5 ~%6) )
16) According to Beadle and Tatum's one gene-one enzyme hypothesis, how many gene(s) is (are) necessary for this pathway?

A) 0


B) 3

C) 2


D) 1

E) It cannot be determined from the pathway.


17) One strain of a diploid organism is homozygous for a recessive allele coding for a defective enzyme a. Another strain is homozygous for a recessive allele coding for a defective enzyme b. Crossing those two strains will result in a strain that would grow on which of the following?

A) a minimal medium supplemented with both A and B

B) a minimal medium supplemented with A

C) a minimal medium supplemented with B

D) All of the above will support the growth of the new strain.
18) Which of the following represents a similarity between RNA and DNA?

A) the presence of uracil

B) the presence of a double-stranded helix

C) nucleotides consisting of a phosphate, sugar, and nitrogen base

D) the presence of an OH group on the 3' carbon of the sugar

E) repair systems that correct genetic code errors


19) A particular triplet of bases in the coding sequence of DNA is AGT. The corresponding codon for the mRNA transcribed is

A) TCA.


B) AGT.

C) AGU.


D) UCA.

E) either UCA or TCA, depending on wobble in the first base.


The following questions refer to Figure 17.1, a table of codons.

Figure 17.1


20) A possible sequence of nucleotides in DNA that would code for the polypeptide sequence phe-leu-ile-val would be

A) 5' TTG-CTA-CAG-TAG 3'.

B) 3' AAA-GAA-TAA-CAA 5'.

C) 5' AUG-CTG-CAG-TAT 3'.

D) 3' AAA-AAT-ATA-ACA 5'.

E) 3' AAC-GAC-GUC-AUA 5'.


21) What amino acid sequence will be generated, based on the following mRNA codon sequence?

5'AUG-UCU-UCG-UUA-UCC-UUG

A) met-arg-glu-arg-glu-arg

B) met-leu-phe-arg-glu-glu

C) met-glu-arg-arg-gln-leu

D) met-ser-leu-ser-leu-ser

E) met-ser-ser-leu-ser-leu
22) A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. What is the sequence in DNA that codes for this peptide?

A) 3' AAA-GGG-TTT-CCC-AAA-GGG

B) 5' ACT-TAC-CAT-AAA-CAT-TAC-UGA

C) 5' GGG-AAA-TTT-AAA-CCC-ACT-GGG

D) 3' AUG-AAA-GGG-TTT-CCC-AAA-GGG

E) 3' UUU-CCC-AAA-GGG-UUU-CCC


23) What is the sequence of a peptide based on the mRNA sequence 5' UUUUCUUAUUGUCUU?

A) leu-pro-asp-lys-gly

B) cyc-phe-tyr-cys-leu

C) leu-cys-tyr-ser-phe

D) phe-ser-tyr-cys-leu

E) phe-leu-ile-met-val


24) A particular triplet of bases in the coding sequence of DNA is AGT. What is the corresponding triplet in the complementary strand of DNA?

A) GAC


B) AGT

C) TCA


D) UCA

E) TCA in eukaryotes, but UCA in prokaryotes


25) Which of the following is correct about a codon? It

A) may code for the same amino acid as another codon.

B) is the basic unit of the genetic code.

C) catalyzes RNA synthesis.

D) consists of two nucleotides.

E) consists of discrete amino acid regions.


26) If the triplet UUU codes for the amino acid phenylalanine in bacteria, then in plants UUU should code for

A) proline.

B) leucine.

C) valine.

D) phenylalanine.

E) cystine.


27) Which of the following is true for both prokaryotic and eukaryotic gene expression?

A) Translation of mRNA can begin before transcription is complete.

B) The mRNA transcript is the exact complement of the gene from which it was copied.

C) RNA polymerase may recognize a promoter region and begin transcription.

D) mRNA is synthesized in the 3' Â 5' direction.

E) After transcription, a 3' poly(A) tail and a 5' cap are added to mRNA.


28) All of the following are transcribed from DNA except

A) exons. B) mRNA. C) rRNA. D) protein. E) tRNA.


29) Which of the following is not involved in transcription?

A) initiation factors

B) RNA polymerase

C) promoter

D) terminator

E) TATA box


30) DNA has two functions it can self-replicate and it can make non-DNA molecules. DNA is capable of these because

A) both DNA and proteins can be synthesized directly at the DNA template.

B) its replication is semiconservative.

C) its nucleotides will form base pairs with both ribose and deoxyribose nucleotides.

D) replication and expression are thermodynamically spontaneous and require no enzymes.

E) its two strands are held together by easily broken electrostatic interactions.


31) In eukaryotic cells, transcription cannot begin until

A) the two DNA strands have completely separated and exposed the promoter.

B) the appropriate transcription factors have bound to the promoter.

C) the 5' caps are removed from the mRNA

D) the DNA introns are removed from the template

E) DNA nucleases have isolated the transcription unit from the noncoding DNA


32) What are the coding segments of a stretch of eukaryotic DNA called?

A) exons

B) introns

C) codons

D) transposons

E) replicons


33) Once transcribed, eukaryotic mRNA typically undergoes substantial alteration that includes

A) fusion into circular forms known as plasmids.

B) linkage to histone molecules.

C) union with ribosomes.

D) excision of introns.

E) fusion with other newly transcribed mRNA.


34) Introns are significant to biological evolution because

A) they protect the mRNA from degeneration.

B) they are translated into essential amino acids.

C) they correct enzymatic alterations of DNA bases.

D) they maintain the genetic code by preventing incorrect DNA base pairings.

E) their presence increases the frequency of recombination.


35) All of the following are directly involved in translation except

A) amino acid-activating enzymes.

B) mRNA.

C) ribosomes.

D) DNA.

E) tRNA.


36) A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is

A) TTT.


B) UUA.

C) UUU.


D) AAA.

E) either UAA or TAA, depending on wobble in the first base.


37) What are ribosomes composed of?

A) both rRNA and protein

B) mRNA, rRNA, and protein

C) two subunits, each consisting of rRNA only

D) mRNA, tRNA, rRNA, and protein

E) two subunits, each consisting of several proteins only


38) The function of the ribosome in polypeptide synthesis is to

A) move tRNA and mRNA during the translocation process.

B) catalyze the addition of amino acids from the tRNAs to the growing polypeptide chain.

C) hold mRNA and tRNAs together.

D) do A and B.

E) do A, B, and C.


39) From the following list, which is the first event in translation in eukaryotes?

A) covalent bonding between the first two amino acids

B) base pairing of activated methionine-tRNA to AUG of the messenger RNA

C) binding of the larger ribosomal subunit to smaller ribosome subunits

D) elongation of the polypeptide

E) Both B and D occur simultaneously.


40) During translation, chain elongation continues until what happens?

A) All tRNAs are empty.

B) The polypeptide is long enough.

C) No further amino acids are needed by the cell.

D) Chain terminator codons occur.

E) The ribosomes run off the end of mRNA.


41) What are polyribosomes?

A) ribosomes associated with more than one tRNA

B) groups of ribosomes reading the same mRNA simultaneously

C) multiple copies of ribosomes found associated with giant chromosomes

D) aggregations of vesicles containing ribosomal RNA

E) ribosomes containing more than two subunits


42) Of the following types of mutations, which one is likely to be the most common?

A) base-pair substitution

B) missense mutation

C) frameshift mutation

D) point mutation

E) nonsense mutation


43) A frameshift mutation could result from

A) a base insertion only.

B) a base deletion only.

C) a base substitution only.

D) deletion of three consecutive bases.

E) either an insertion or a deletion of a base.


44) When a nucleotide pair is lost from the middle of a gene during the process of transcription, what happens?

A) Normal termination does not occur; transcription continues indefinitely.

B) There is little effect on the protein being synthesized due to redundancy of the genetic code.

C) A signal-recognition particle moves in to correct coding errors.

D) snRNPs splice and then remove incorrect amino acids.

E) The reading frame is shifted, producing a nonfunctional polypeptide.


45) What type of bonding is responsible for maintaining the shape of the tRNA molecule?

A) van der Waals interactions between hydrogen atoms

B) hydrogen bonding between base pairs

C) ionic bonding between phosphates

D) covalent bonding between sulfur atoms

E) peptide bonding between amino acids


46) What is the relationship among DNA, a gene, and a chromosome?

A) A gene contains hundreds of chromosomes, which are composed of protein.

B) A gene contains hundreds of chromosomes, which are composed of DNA.

C) A chromosome contains hundreds of genes, which are composed of DNA.

D) A chromosome contains hundreds of genes, which are composed of protein.

E) A gene is composed of DNA, but there is no relationship to a chromosome.


47) In eukaryotic cells, transcription cannot begin until

A) the appropriate transcription factors have bound to the promoter.

B) DNA nucleases have isolated the transcription unit from the noncoding DNA.

C) the two DNA strands have completely separated and exposed the promoter.

D) the 5' caps are removed from the mRNA.

E) the DNA introns are removed from the template.


48) Which of the following is not true of a codon?

A) It may code for the same amino acid as another codon does.

B) It never codes for more than one amino acid.

C) It extends from one end of a tRNA molecule.

D) It is the basic unit of the genetic code.

E) It consists of three nucleotides.


49) The anticodon of a particular tRNA molecule is

A) complementary to the corresponding mRNA codon.

B) catalytic, making the tRNA a ribozyme.

C) complementary to the corresponding triplet in rRNA.

D) changeable, depending on the amino acid that attaches to the tRNA.

E) the part of tRNA that bonds to a specific amino acid.


50) Which of the following is not true of RNA processing?

A) Ribozymes may function in RNA splicing.

B) RNA splicing may be catalyzed by spliceosomes.

C) A primary transcript is often much longer than the final RNA molecule that leaves the nucleus.

D) The presence of introns may facilitate crossing over between regions of a gene that code for polypeptide domains.

E) Exons are excised and hydrolyzed before mRNA moves out of the nucleus.


ESSAY. Write your answer in the space provided or on a separate sheet of paper.

Answer the following on a separate sheet of paper (20 pts)

51) Science, Technology, and Society Our civilization generates many potentially mutagenic chemicals (pesticides, for example). Some argue that civilization modifies the environment in ways that increase exposure to other mutagens, notably UV radiation. What role should government play in identifying mutagens and regulating their release to the environment?



1) Answer C
2) Answer A
3) Answer C
4) Answer D
5) Answer A
6) Answer E
7) Answer A
8) Answer D
9) Answer E
10) Answer C
11) Answer D
12) Answer E
13) Answer C
14) Answer B
15) Answer E
16) Answer C
17) Answer B
18) Answer C
19) Answer D
20) Answer B
21) Answer E
22) Answer A
23) Answer D
24) Answer C
25) Answer A
26) Answer D
27) Answer C
28) Answer D
29) Answer A
30) Answer C
31) Answer A, B
32) Answer A
33) Answer D
34) Answer E
35) Answer D
36) Answer D
37) Answer A
38) Answer E
39) Answer B
40) Answer D
41) Answer B
42) Answer D
43) Answer E
44) Answer E
45) Answer B
46) Answer C
47) Answer A
48) Answer C
49) Answer A
50) Answer E
51) Answer
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