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Which of the following statements about aneuploidy is false?


A) It results from chromosomal nondisjunction.
B) It does not occur in humans.
C) An individual with an extra chromosome is trisomic.
D) Trisomies are common in human zygotes.
E) A piece of one chromosome may translocate to another chromosome.

F) All of the above
G) D) and E)

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To divide, cells must be stimulated by external chemical signals called _______.

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Genetic recombination occurs during


A) prophase of meiosis I.
B) the interphase preceding meiosis II.
C) the mitotic telophase.
D) fertilization.
E) the formation of somatic cells.

F) A) and B)
G) A) and E)

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Cells that do not divide are usually arrested in


A) S.
B) G1.
C) G2.
D) M.
E) prophase.

F) A) and E)
G) A) and D)

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Which of the following statements about cyclin-dependent kinases (Cdk's) or cyclin is false?


A) Different Cdk's act at different points in the cell cycle.
B) A Cdk can catalyze the phosphorylation of retinoblastoma protein.
C) Phosphorylated retinoblastoma protein is inactive.
D) Cdk's use ATP as a substrate.
E) Cyclin is made continuously during the cell cycle.

F) A) and B)
G) C) and E)

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Chromatin consists of


A) DNA and histones.
B) DNA, histones, and many other nonhistone proteins.
C) mostly RNA and DNA.
D) RNA, DNA, and nonhistone proteins.
E) DNA only.

F) C) and D)
G) C) and E)

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The energy to move chromosomes during mitosis is provided by


A) centrioles.
B) DNA polymerization.
C) migration of the centrosomes.
D) formation of the cell plate.
E) ATP.

F) B) and D)
G) A) and E)

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Chloroplasts contain DNA and reproduce by fission, much like bacteria. DNA replication is not synchronized with chloroplast division. Yet, after division, both daughter chloroplasts contain DNA. How?


A) There are a large number of DNA molecules per chloroplast.
B) The DNA is organized into nucleosomes.
C) There is a mitotic spindle in dividing chloroplasts.
D) Chloroplast DNA is circular.
E) None of the above

F) A) and E)
G) A) and D)

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The event in the cell division process that clearly involves microfilaments is


A) chromosome separation during anaphase.
B) movement of chromosomes to the metaphase plate.
C) chromosome condensation during prophase.
D) disappearance of the nuclear envelope during prophase.
E) cytokinesis in animal cells.

F) None of the above
G) A) and B)

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The four haploid nuclei found at the end of meiosis differ from one another in their exact genetic composition. Some of this difference is the result of


A) cytokinesis.
B) replication of DNA during the S phase.
C) separation of sister chromatids at anaphase II.
D) spindle formation.
E) crossing over during prophase I.

F) C) and D)
G) A) and E)

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Centrosomes


A) are constricted regions of phase chromosomes.
B) determine the plane of cell division.
C) are the central region of the cell.
D) are the region where the membrane constricts during cytokinesis.
E) are part of cilia.

F) B) and D)
G) A) and C)

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For a prokaryote cell to divide, which of the following must occur?


A) A reproductive signal, replication, segregation of DNA, and cytokinesis
B) DNA replication, crossing over, and segregation of DNA
C) DNA replication and segregation of DNA
D) Cell growth and cytokinesis
E) DNA replication, segregation of DNA, and cytokinesis

F) B) and E)
G) A) and C)

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Which of the following is true of benign tumors?


A) The cells do not resemble the cells of the parent tissue.
B) The cells of the tumor are often irregular, with nuclei of various sizes and shapes.
C) The cells grow more rapidly than the cells surrounding it.
D) They often metastasize.
E) They are not cancer.

F) A) and E)
G) A) and D)

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The diagnosis of Down syndrome is made by examining the individual's


A) spores.
B) karyotype.
C) chromatin.
D) nucleosomes.
E) kinetochores.

F) A) and C)
G) C) and D)

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Apoptosis


A) occurs in all cells.
B) involves the formation of the plasma membrane.
C) does not occur in an embryo.
D) is a series of programmed events resulting in cell death.
E) is the same as necrosis.

F) A) and B)
G) B) and E)

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Nucleosomes


A) are made of chromosomes.
B) consist entirely of DNA.
C) consist of DNA wound around a histone core.
D) are present only during mitosis.
E) are present only during prophase.

F) A) and D)
G) A) and E)

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The milestone event that defines entry into prometaphase is loss of the _______.

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Which statement about cytokinesis is true?


A) In animals, a cell plate forms.
B) In plants, it is initiated by furrowing of the membrane.
C) It follows mitosis.
D) In plant cells, actin and myosin play an important part.
E) It is the division of the nucleus.

F) C) and D)
G) A) and B)

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Knowledge of the cell cycle has led to improved means of treating cancer. The drug 5-fluorouracil blocks the synthesis of thymine. This drugs inhibits the cell cycle at the end of


A) G1.
B) G2.
C) S.
D) prophase.
E) metaphase.

F) A) and E)
G) A) and D)

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The basic structure of chromatin has sometimes been referred to as beads on a string of DNA. These beads are called


A) chromosomes.
B) chromatids.
C) supercoils.
D) interphases.
E) nucleosomes.

F) A) and E)
G) C) and E)

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