Download BCOR 011, Exam 3

BCOR 011, Exam 3
Name____
KEY_________
Section __________
Multiple Choice: Select the best possible answer.
1. A parent cell divides to form two genetically identical daughter cells in the nuclear process of
mitosis. For mitosis to take place
a. the parent cell must first be fertilized.
b. the parent cell must replicate all its chromosomes prior to mitosis
c. the parent cell must replicate its DNA during telophase
d. the parent cell must divide its DNA in half so that each daughter cells
gets only the genetic information it needs
e. the parent cell must stop all metabolic functions before entering the interphase
that precedes mitosis
2. At the end of mitosis, each daughter cell has
a. DNA that is identical to that of the parent cell
b. twice the DNA and half the cytoplasm of the parent cell
c. twice the cytoplasm and the same amount of DNA as the parent cell
d. half the DNA and half the cytoplasm of the parent cell
e. a new combination of chromosomes when compared to the parent cell
3. A 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
4. The microtubules of the mitotic spindle attach to a specialized structure in the chromosome
called the
a. kinetochore
b. centriole
c. metaphase plate
d. aster
e. centrosome
5. A certain species of animal has six pairs of chromosomes. How many molecules of DNA do
the nuclei of this animal have in the G2 phase?
a. 3
b. 6
c. 12
d. 24
e. 48
6. In animals, cytokinesis occurs when
a. microtubules pull the cell membrane into a cleavage furrow
b. immediately before mitosis
c. when vesicles from the Golgi body build up to divide the cell in two
d. when G2 is complete
e. when a ring of actin and myosin filaments (microfilaments) contracts
7. The first gap in the cell cycle (G1) corresponds to
a. normal growth and functioning
b. the period in which DNA is being replicated
c. the beginning of mitosis
d. the stage between DNA replication and the M phase
e. the stage the cell enters when it loses its ability to divide
8. The mitotic spindle is a microtubular structure that is involved in
a. splitting of centromeres in anaphase
b. triggering the condensation of chromosomes
c. disassembly of the nucleolus
d. fragmentation of the nuclear envelope
e. separation of sister chromatids
9. Metaphase is characterized by
a. aligning of chromosomes on the metaphase plate
b. splitting of centromeres
c. cytokinesis
d. disassembly of the nuclear envelope
e. a doubling in the number of chromosomes
10. When dividing cells are examined under a light microscope, chromosomes first become
visible during
a. interphase
b. the S phase
c. prophase
d. G1
e. G2
11. The M-phase checkpoint is designed to make sure all chromosomes are attached to the mitotic
spindle. In which stage of mitosis would those cells be most likely to arrest?
a. interphase
b. telophase
c. prophase
d. prometaphase
e. metaphase
12. If a cell has accumulated DNA damage, it is unlikely to
a. pass the G2 checkpoint
b. activate DNA repair enzymes
c. enter G1 from mitosis
d. synthesize cyclin-dependent kinases
e. go through apoptosis
The following questions consist of phrases or sentences related to the control of cell division.
For each one select the term below that is most closely related to the statement. Each term may
be used once, more than once, or not at all.
a. PDGF
b. MPF
c. Protein kinase
d. Cyclin
e. CdK
13. One of the external signals involved in regulating the cell cycle. It is released in the vicinity
of an injury
a
b
c
d
e
14. A general term for enzymes that activate or inactivate other proteins by phosphorylating them
a
b
c
d
e
15. A protein maintained at constant levels throughout the cell cycle that requires cyclin to
become catalytically active
a
b
c
d
e
16. Triggers the cell’s passage past the G2 checkpoint into mitosis
a
b
c
d
e
17. 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 suffer density-dependent
inhibition
e. cancer cells are always in the M-phase of the cell cycle
18. Assume that a particular human cell is examined under a microscope and it contains 22
autosomic chromosomes and a Y chromosome. The cell is most likely to be
a. a somatic cell of a male
b. a somatic cell of an individual suffering from Downs’s syndrome
c. a fertilized egg (a zygote)
d. a somatic cell of a female
e. a sperm
19. Homologous chromosomes move to opposite poles of a dividing cell during
a. mitosis
b. meiosis I
c. meiosis II
d. fertilization
e. none of the above
20. The DNA content of a diploid cell in the G1 phase of a meiotic interphase is X. The DNA
content of a meiotic metaphase II cell from the same organism would be
a. 0.25 X
b. 0.5 X
c. X
d. 2 X
e. 4 X
21. 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
22. At which stage of meiosis is the chromosome number typically reduced from 2n to n
a. meiosis II
b. metaphase II
c. interphase
d. mitosis
e. meiosis I
23. Meiosis II is similar to mitosis in that
a. homologous chromosomes synapse
b. DNA replicates immediately before the division
c. the daughter cells are diploid
d. sister chromatids separate during anaphase
e. the chromosome number is reduced
24. Crossing-over usually contributes to genetic variation by exchanging chromosomal segments
between
a. sister chromatids of a chromosome
b. chromatids of non-homologous chromosomes
c. non-sister chromatids of homologous chromosomes
d. non-homologous chromosomes
e. autosomes and sex chromosomes
25. What is a tetrad?
a. the “X” that forms when crossing-over occurs
b. a group of four chromatids produced when homologs synapse
c. the four points where homologous chromosomes touch as they synapse
d. the group of four genetically identical daughter cells produced by mitosis
e. the group of four haploid cells produced by meiosis
26. 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 single-celled organisms
27. At the end of meiosis I, each chromosome consist of
a. a homologous chromosome pair
b. four copies of a DNA molecule
c. one copy of a DNA molecule
d. two chromatids
e. a pair of polar microtubules
28. 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
29. At which stage of mitosis are chromosomes photographed in the preparation of a karyotype?
a. prophase
b. metaphase
c. anaphase
d. telophase
e. interphase
30. Crossing-over occurs during which phase of meiosis?
a. prophase I
b. anaphase I
c. telophase I
d. prophase II
e. metaphase II
31. In 1928, Griffith injected S (smooth) bacteria into mice, and the mice died. When he injected
living R (rough) bacteria into mice, the mice lived. When he injected heat-killed smooth bacteria
into mice, the mice lived. What was the result when he mixed heat-killed S bacteria with live R
bacteria and injected this mixture into mice?
a. the mice lived
b. the mice died indicating that heat-killed S bacteria came back to life
c. the mice lived, and living S bacteria could be obtained from the tissues of living
mice
d. the mice died, indicating that DNA replicated semi-conservatively
e. the mice died, and living S cells could be isolated from the tissues of the dead mice
32. Assume that you have determined the percentages of bases in DNA samples from variety of
organisms, each having DNA in the usual double-stranded form. What relationship would you
expect to find in the percentage data?
a. A = C
b. A = G
c. C = T
d. A + C = G + T
e. A + T = G + C
33. DNA replication is said to be semi-conservative because
a. half of the DNA in a new cell comes from one gamete and other half from the other
b. the same process of DNA replication is used by all organisms
c. the number of nucleotides within genes remain constant
d. each DNA molecule is composed of one old strand and one new strand
e. the total amount of DNA within an individual remains the same
34. Where and how are Okasaki fragments synthesized?
a. at the leading strand, oriented in a 5’ to 3’ direction
b. at the leading strand, oriented in a 3’ to 5’ direction
c. at the lagging strand, oriented in a 5’ to 3’ direction
d. at the lagging strand, oriented in a 3’ to 5’ direction
e. none of the above
35. Once DNA strands are separated by DNA Helicase, ____________ block the reformation of a
double helix by the template strands
a. RNA primer strands
b. topoisomerase
c. single-strand binding proteins
d. RNA polymerase complexes
e. DNA polymerase III
36. All of the following can be determined directly from X-ray diffraction photographs of
crystallized DNA except the
a. diameter of the helix
b. sequences of nucleotides
c. spacing of the bases along the helix
d. number of strands in the helix
e. helical shape of DNA
37. What kind of chemical bond is found between paired bases of the DNA double helix?
a. hydrogen
b. ionic
c. covalent
d. sulfhydryl
e. phosphate
38. Suppose one were provided with an actively dividing culture of E. coli bacteria to which
radioactive thymine has 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 will have radioactive DNA
b. Neither of the two daughter cells will 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 will be radioactive
39. What determines the nucleotide sequence of the newly synthesize strand during DNA
replication?
a. the particular DNA polymerase catalyzing the reaction
b. the relative amounts of the four nucleotides in the cell
c. the nucleotide sequence of the template strand
d. the primase used in the reaction
e. the leading strand
40. What is the role of DNA ligase in the elongation of the lagging strand during DNA
replication?
a. synthesize RNA nucleotides to make primer
b. catalyze the lengthening of telomeres
c. join Okasaki fragments together
d. unwind the parental double helix
e. stabilize the unwound parental DNA
41. In eukaryotic cells, each chromosome has
a. one origin of replication
b. two origins of replication
c. many origins of replication
d. only one origin of replication per nucleus
e. none of the above
42. The enzyme that removes the RNA primers is called
a. DNA ligase
b. primase
c. helicase
d. Topoisomerase
e. DNA polymerase I
43. The 3’ end of a DNA strand is the place in the molecule where
a. the phosphate group is not bound to another nucleotide
b. both DNA strands end opposite each other
c. polymerase builds the primer
d. there is a free OH group at the 3’ carbon of deoxyribose
e. three adenine nucleotides are present
44. A codon
a. consist of two nucleotides
b. may code for the same amino acid as another codon
c. consists of amino acids
d. catalyzes RNA synthesis
e. is found in all eukaryotes but not in prokaryotes
45. If the triplet CCC codes for the amino acid proline in bacteria, then in plants CCC should
code for
a. leucine
b. valine
c. cystine
d. phenyl amine
e. proline
46. RNA polymerase II uses the ______ DNA template to synthesize a ______ mRNA
a. 5’ → 3’, 5 → 3’
b. 3’ → 5’, 3’ → 5’
c. 3’ → 5’, 5’ → 3’
d. 5’ → 3’, 3’ → 5’
e. example of all these have been found
47. Transcriptions is the process of
a. synthesizing a DNA molecule from an RNA template
b. assembling ribonucleotides into an RNA molecule without a template
c. synthesizing an RNA molecule using a DNA template
d. synthesizing a protein using information from a messenger RNA
e. replicating a single-stranded DNA molecule
48. A transcription start signal is called a (an)
a. initiation codon
b. promoter
c. origin
d. operator
e. nonsense codon
49. Which of the following is a post-transcriptional modification of mRNA found in eukaryotes?
a. a 5’ cap
b. a 3’ cap
c. a poly T tail
d. polyadenylation of the 5’ end
e. none of the above
50. Exons are
a. spliced out of the primary (original) transcript
b. spliced together from the original transcript
c. spliced to introns to form the final transcript
d. much larger than introns
e. larger than the original coding region
51. Transcription factors are
a. RNA sequences that bind to RNA polymerase
b. DNA sequences that regulate up transcription
c. proteins that bind to DNA near the promoter sequence
d. polysaccharides that bind to the transcripts
e. enzymes that splice exons and introns
52. Eukaryotic protein-coding genes differ from their prokaryotic counterparts in that only
eukaryotic genes
a. are double-stranded
b. are present in only a single copy
c. contain introns
d. have a promoter
e. are transcribed into mRNA