Download Exam 3 Key

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BCOR 11, Exam 3
Name ______________________________
Date _____________________
Multiple choice: Select the BEST possible answer.
1. The centromere is a region in which
a. chromatids are attached to one another *
b. metaphase chromosomes become aligned
c. chromosomes are grouped during telophase
d. the nucleus is located prior to mitosis
e. new spindle microtubules form
2. The amount of DNA present in a cell would be the least in which of the following phases
of the cell cycle?
a. anaphase
b. interphase
c. metaphase
d. prophase
e. telophase *
3. A cell containing 92 chromatids at metaphase of mitosis would, at the completion of
mitosis, produce two nuclei containing how many chromosomes?
a. 12
b. 16
c. 23
d. 46 *
e. 92
4. Scientists isolate cells at various stages of the cell cycle. They find a group of cells that
have 1.5 times more DNA that the parent cell has during its normal growth and
functioning stage. These cells are in
a. the process of cytokinesis
b. the G2 phase of the cell cycle
c. M phase
d. S phase *
e. G0
5. Nerve cells lose their ability to undergo mitosis. Instead they are permanently stuck in
a. G2
b. G0 *
c. S of interphase
d. Meiosis
e. Metaphase
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6. The M phase checkpoint is designed to make sure all chromosomes are attached to the
mitotic spindle. In which stage would these cells be most likely to arrest?
a. telophase
b. prophase
c. metaphase *
d. either b or c
e. none of the above
7. A cell with its chromosomes lined up across the middle of the cell is in
a. prophase
b. S
c. Metaphase *
d. anaphase
e. telophase
8. During mitosis it is necessary for the nuclear envelope of the parent cell to disintegrate.
This is accomplished at least in part by phosphorylation of proteins associated with the
nuclear envelope. If the enzyme responsible for that event is inhibited, at which phase of
mitosis are cells likely to arrest?
a. Prophase *
b. metaphase
c. anaphase
d. telophase
e. none of the above, mitosis never arrests
9. Where do the microtubules of the spindle originate during mitosis in both plant and
animal cells?
a. centromere
b. centrosome *
c. centriole
d. chromatid
e. kinetochore
10. The formation of a cell plate is beginning across the middle of a cell and nuclei are reforming at opposite ends of the cell. What kind of cell is this?
a. an animal cell in metaphase
b. an animal cell in telophase
c. an animal cell undergoing cytokinesis
d. a plant cell in metaphase
e. a plant cell undergoing cytokinesis *
11. One difference between a cancer cell and a normal cell is that
a. the cancer cell is unable to synthesize DNA
b. the cell cycle of the cancer cell is arrested at the S phase
c. cancer cells continue to divide even when they are tightly packed together *
d. cancer cells cannot function properly because they exhibit density-dependent
inhibition (contact inhibition)
e. cancer cells are always in the M phase of the cell cycle
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12. What is a karyotype?
a. the set of unique physical characteristics that define an individual
b. the collection of all mutations present within a genome
c. a unique combination of chromosomes found in a gamete
d. a system of classifying cell nuclei
e. a display of every pair of homologous chromosomes within a cell organized
according to size and shape *
13. If a typical diploid somatic cell has 32 chromosomes, how many chromosomes are
expected in each gamete of that organism?
a. 32
b. 64
c. 16 *
d. 0
e. 46
14. After telophase I of meiosis, what is the chromosomal makeup or each daughter cell?
a. diploid, and the chromosomes of each have a single chromatid
b. diploid, and the chromosomes are each composed of two chromatids
c. haploid, and the chromosomes are each composed of single chromatids
d. haploid, and the chromosomes are each composed of two chromatids *
e. all of the above depending on the type of cell that entered meiosis
15. Genetic variation, resulting from sexual reproduction, offers more opportunity for
offspring to survive in changing environments. What two aspects of meiosis provide
sources of such variation?
a. mutation and fertilization
b. crossing over and separation (segregation) of homologous chromosomes
c. separation of homologous chromosomes and independent assortment of
chromosomes
d. crossing over and independent assortment of chromosomes *
e. mutation and separation of homologous chromosomes
16. Which of the following occurs during meiosis II but DOES NOT occur as part of meiosis I?
a. crossing over between homologous chromosomes
b. separation of homologous chromosomes
c. synapsis of homologous chromosomes
d. separation of sister chromosomes *
e. migration of the chromosomes to the center of the cell
17. Meiosis can occur
a. in all organisms
b. only when an organism is diploid *
c. only in multicellular organisms
d. only in haploid organisms
e. only in a single-celled organism
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18. Chromosome number is reduced during meiosis because the process consists of
a. two cell divisions without ay chromosome replication
b. one cell division without chromosome replication
c. two cell divisions in which half of the chromosomes are destroyed
d. two cell divisions and only a single round of chromosome replication *
e. four cell divisions with no chromosome replication
19. Which of the following is TRUE of a species that has a chromosome number of 2n = 16?
a. the species is diploid with 32 chromosomes
b. the species has 16 sets of chromosomes
c. there are 8 homologous pairs of chromosomes *
d. during the S phase of the cell cycle there will be 32 separate chromosomes
e. the gametes from this species have 4 chromosomes each
20. Crossing over occurs during which phase of meiosis?
a. prophase I *
b. anaphase I
c. telophase I
d. prophase II
e. metaphase II
Use the following key to answer questions 27 through 31. Each answer may be used once,
more than once, or not at all.
a.
b.
c.
d.
e.
The statement is true for mitosis only.
The statement is true for meiosis I only.
The statement is true for meiosis II only.
The statement is true for meiosis I and mitosis.
The statement is true for meiosis II and mitosis.
21. A cell divides to produce two daughter cells that are genetically identical.
a. *
b.
c.
d.
e.
22. Homologous chromosomes synapse and crossing over occurs.
a.
b. *
c.
d.
e.
23. Centromeres divide (uncouple) and sister chromatids are separated from each other.
a.
b.
c.
d.
e. *
24. Independent assortment of chromosomes occurs.
a.
b. *
c.
d.
e.
25. The process is preceded by replication of DNA.
a.
b.
c.
d. *
e.
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26. In the Hershey and Chase experiment, the pellet in the centrifuge tube was radioactive
after bacteria had been infected with 32P labeled viruses and centrifuged. Why?
a. bacteria were precipitated during centrifugation and they had incorporated
radioactive proteins from the virus into their cell membranes
b. bacteria were precipitated during centrifugation and they had incorporated
radioactive proteins into their DNA
c. viruses were precipitated during centrifugation and they had incorporated
proteins from the bacteria
d. viruses were precipitated during centrifugation and they had incorporated
radioactive DNA from the bacteria
e. bacteria were precipitated during centrifugation and they had incorporated
radioactive DNA from the viruses *
27. In the 1920’s Griffith discovered a species of bacteria that caused pneumonia in mice. In
his experiments mice were injected with different strains of treated and untreated
bacteria. Which of the following is NOT LIKELY to have occurred in a Griffith series
of experiments?
a. mice injected with living S (virulent) strain die
b. mice injected with living R (non-virulent) strain live
c. mice injected with heat-killed S live
d. mice injected with living R plus heat-killed S die
e. mice injected with living S plus heat killed R live *
28. Given the structure of DNA, what component of that structure is most directly associated
with encoding genetic information?
a. the sequence of phosphates
b. nitrogenous bases and their sequence *
c. the arrangement of phosphodiester linkages
d. the order of the deoxyribose sugars
e. all of the above are correct
29. DNA replication is said to be semiconservative because
a. half of the DNA in one cell comes from one gamete and the other half from the
other gamete
b. the same process of DNA replication is used by all organisms
c. the number of nucleotides within genes remains constant
d. each new DNA molecule is composed of one old strand and one new strand *
e. the total amount of DNA within an individual remains the same
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30. During DNA replication, DNA ligase is most active on the lagging strand. This is
because
a. the lagging strand has more short segments than the leading strand and those
short segments are joined together by DNA ligase *
b. DNA in the lagging strand is synthesized in the 3’----5’ direction
c. the lagging strand has no RNA primase activity, it is replaced by the DNA ligase
d. the lagging strand requires DNA ligase to couple the RNA primer to the Okasaki
fragments
e. the lagging strand is synthesized more slowly and the DNA ligase speeds up the
DNA polymerase
31. Which statement describes the base pairing in nucleic acids?
a. purine bases always pair with other purine bases
b. purine bases only pair with pyrimidine bases *
c. adenine cannot pair with either uracil of thymine
d. hydrogen bonding can only occur between pyrimidines bases
e. guanine pairs with adenine
32. Which of the following is involved in the linking of the two strands of DNA?
a. covalent bonding between the sugar and nitrogenous bases
b. covalent bonding between the sugar and the phosphate groups
c. covalent bonding between adjacent sugar groups
d. hydrogen bonding between the nitrogenous bases *
e. hydrogen bonding between adjacent sugar groups
33. Suppose one were provided with an actively dividing culture of E. coli bacteria to which
radioactive thymidine had been added. What would happen if a cell replicated once in
the presence of this radioactive base?
a. one of the daughter cells, but not the other, would have radioactive DNA
b. neither of the two daughter cells would be radioactive
c. all four bases of the DNA would be radioactive
d. radioactive thymine would pair with non-radioactive guanine
e. DNA in both daughter cells would be radioactive *
34. What is the function of DNA polymerase?
a. to unwind the DNA helix during replication
b. to seal the broken ends of DNA strands
c. to add nucleotides to the end of a growing DNA strand *
d. to degrade damaged DNA molecules
e. to rejoin the two DNA strands (one old, one new) after replication
35. A new DNA strand elongates only in the 5’ to 3’ direction because
a. DNA polymerase begins adding nucleotides at the 5’ end of the template
b. Okasaki fragments prevent elongation in the 3’ to 5’ direction
c. the polarity of the DNA molecules prevents the addition of nucleotides at the 3’
end
d. replication must progress toward the replication fork
e. DNA polymerase can only add nucleotides to the free 3’ end *
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36. Which of the following help to hold the DNA strand apart while they are being
replicated?
a. primase
b. ligase
c. DNA polymerase
d. single-strand binding proteins *
e. exonuclease
37. A eukaryotic cell lacking telomerase would
a. have a high probability of becoming cancerous
b. produce Okasaki fragments
c. be unable to repair thymine dimers
d. undergo a reduction in chromosome length *
e. be highly sensitive to sunlight
38. A codon
a. consists of two nucleotides
b. may code for the same amino acid as another codon *
c. consists of discrete amino acid regions
d. catalyzes RNA synthesis
e. is found in all eukaryotes, by not in prokaryotes
39. The genetic code is fairly consistent among all organisms. The term often used to
describe such consistency in the code is
a. universal *
b. exceptional
c. redundant
d. ambiguous
e. overlapping
40. The TATA box has all the following characteristics EXCEPT
a. it is both transcribed and translated *
b. it is upstream of most genes
c. it is part of the binding site for the RNA polymerase
d. it is part of a consensus (common) region
e. it is typical of eukaryotic genes
41. How can a eukaryotic gene be longer than an mRNA produced by that gene?
a. the exons have been spliced out during mRNA processing
b. the DNA is a double stranded structure while the RNA is single stranded
c. there are more amino acids coded for by the DNA than by the mRNA
d. introns have been spliced out during mRNA processing *
e. when the mRNA is produced it is highly folded and therefore shorter
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42. Select three post-transcriptional modifications seen in the maturation of mRNA in
eukaryotes
a. 5’capping, 3’ polyA tail addition, splicing *
b. 3’capping, 5’ polyA addition, splicing
c. removal of exons, insertion of introns, capping
d. 5’ polyA tail addition, insertion of introns, capping
e. heteroduplex formation, base modification, capping
43. During splicing which molecular component of the spliceosome catalyzes the excision
reaction?
a. RNA *
b. DNA
c. protein
d. lipid
e. sugar
44. The function of the ribosome in polypeptide synthesis is to
a. hold mRNA and tRNA together
b. catalyze the addition of amino acids from the charged tRNA to the growing
polypeptide chain
c. move along the mRNA and eject tRNA during the translocation process
d. a and b only
e. a, b, and c *
45. From the following list, which is the first event in translation in eukaryotes?
a. elongation of the polypeptide
b. base pairing of activated methionine tRNA to AUG of the messenger RNA *
c. binding of the larger ribosomal subunit to smaller ribosomal subunits
d. covalent bonding between the first two amino acids
e. both b and d occur simultaneously
46. During translation, chain elongation continues until what happens?
a. no further amino acids are needed by the cell
b. all tRNAs are empty
c. the polypeptide is long enough
d. a stop codon is encountered *
e. the ribosomes run off the end of the mRNA
47. As a ribosome translocates along an mRNA molecule by one codon, which of the
following occurs?
a. the tRNA that was in the A site moves into the P site
b. the tRNA that was in the P site moves into the A site
c. the tRNA that was in the P site moves to the E site and is released
d. the tRNA that was in the A site departs from the ribosome
e. both a and c are correct *
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48. What is the effect of a nonsense mutation in a gene?
a. it changes an amino acid in the encoded protein
b. it has no effect on the amino acid sequence of the encoded protein
c. it introduces a stop codon into the mRNA *
d. it alters the reading frame of the mRNA
e. it prevents introns from being expressed
49. Translation occurs in
a. the cytoplasm *
b. a lysosome
c. the nucleus
d. the golgi apparatus
e. the nucleoplasm
For Questions 50 – 52 assume that the nucleotide sequence of a mRNA strand is
AUCUACGGG.
50. The anticodon of the tRNA specified by the first codon in the mRNA is:
a. UAC *
b. AUG
c. TAC
d. GGG
e. UCU
51. What would be the nucleotide sequence of the sense strand of DNA?
a. TAGATGCCC *
b. ATCTACGGG
c. AUCUACGGG
d. CGTCGGAAA
e. UTCTUGCCC
52. What would be the nucleotide sequence of the antisense strand of DNA?
a. TAGATGCCC
b. ATCTACGGG *
c. AUCUACGGG
d. CGTCGGAAA
e. UTCTUGCCC