Chapter 11 Flashcards
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.
C
Which statement about the cell cycle is not true?
A. It consists of interphase, mitosis, and cytokinesis.
B. The cell’s DNA replicates during G1.
C. A cell can remain in G1 for weeks or much longer.
D. DNA is not replicated during G2.
E. Cells enter the cell cycle as a result of internal or external signals.
B
Which statement about eukaryotic chromosomes is not true?
A. They sometimes consist of two chromatids.
B. They sometimes consist only of a single chromatid.
C. They normally possess a single centromere.
D. They consist only of proteins.
E. During metaphase they are visible under the light microscope.
D
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.
C
Which statement about mitosis is not true?
A. A single nucleus gives rise to two identical daughter nuclei.
B. The daughter nuclei are genetically identical to the parent nucleus.
C. The centromeres separate at the onset of anaphase.
D. Homologous chromosomes synapse in prophase.
E. The centrosomes organize the microtubules of the spindle fibers.
D
In meiosis,
A. meiosis II reduces the chromosome number from diploid to haploid.
B. DNA replicates between meiosis I and meiosis II.
C. the chromatids that make up a chromosome in meiosis II are identical.
D. each chromosome in prophase I consists of four chromatids.
E. homologous chromosomes separate from one another in anaphase I.
E
In meiosis,
A. a single nucleus gives rise to two daughter nuclei.
B. the daughter nuclei are genetically identical to the parent nucleus.
C. the centromeres separate at the onset of anaphase I.
D. homologous chromosomes synapse in prophase I.
E. no spindle forms.
D
An animal has a diploid chromosome number of 12. An egg cell of that animal has 5 chromosomes. The most probable explanation is
A. normal mitosis.
B. normal meiosis.
C. nondisjunction in meiosis I.
D. nondisjunction in meiosis I or II.
E. nondisjunction in mitosis.
D
The number of daughter chromosomes in a human cell (diploid number 46) in anaphase II of meiosis is
A. 2.
B. 23.
C. 46.
D. 69.
E. 92.
C
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.
D
Which of the following statements regarding cell division in prokaryotes (shown) is false?
A. The bacterial chromosome is circular.
B. Prokaryotic cells undergo mitosis, but not meiosis.
C. The initial step in prokaryotic cell division involves replication of the single chromosome.
D. Cytokinesis starts immediately after DNA replication in rapidly growing cells.
E. Cell division in some prokaryotes can occur in as little as 20 minutes.
B
Which of the following pairings regarding the eukaryotic cell cycle (shown) is false?
A. M phase: Mitosis and Cell Division.
B. G1 phase: Gap 1; cell begins preparation for DNA replication.
C. S phase: Synthesis stage; DNA is replicated.
D. G2 phase: Gap 2; cell begins preparation for mitosis.
E. G0 phase: Gap 0; separation of sister chromatids occurs.
E
Which of the following statements about protein signals involved in the control of the cell cycle (shown) is false?
A. Transition from G1 to S and G2 to M depends on the phosphorylation of certain key proteins by cyclin-dependent kinase or Cdk.
B. Cdk’s must be bound with a specific cyclin to be active as kinases.
C. In humans, cyclin D-cdk4 triggers the G1-to-S transition, whereas cyclin B-cdk1 triggers the G2-to-M transition.
D. External control mechanisms involving growth factors and hormones can activate cells that are arrested or are cycling slowly.
E. The phosphorylation of retinoblastoma protein effectively inhibits cell division.
E
During formation of the mitotic spindle, there is (are) _______ centriole(s) while each chromosome consists of _______ chromatid(s), _______ centromere(s), and _______ kinetochore(s).
A. 1; 1; 1; 2
B. 1; 2; 1; 2
C. 2; 2; 1; 2
D. 2; 2; 2; 2
E. 2; 2; 1; 4
C
Complete the following sentence for the cell shown. This cell is in _______ of mitosis and has _______ copies of each chromosome.
A. prometaphase; two
B. prometaphase; four
C. prometaphase; eight
D. anaphase; two
E. anaphase; four
A
Which of the following statements regarding the stage of mitosis shown here is false?
A. All chromosomes have aligned at the equatorial plate.
B. Chromosomes are maximally condensed in this stage.
C. At the end of this stage, the chromatid pairs separate simultaneously.
D. The molecule cohesin holds the sister chromatids together in this stage.
E. The separation of sister chromatids requires the digestion of cohesin by the enzyme securin.
E
Which of the following statements regarding mitosis is true?
A. Only diploid cells can divide mitotically.
B. Crossing over can occur during prophase of mitosis.
C. Cells produced by mitosis are almost always genetically identical.
D. Each mitotically produced cell has one-fourth the mass of DNA present in the parent cell.
E. At metaphase, each chromosome has a single kinetochore attached at the centromere.
C
Complete the following sentence about the photomicrograph shown. This is _______ cell, undergoing _______, with the formation of a _______.
A. an animal; apoptosis; division furrow
B. an animal; cytokinesis; division furrow
C. an animal; interkinesis; division furrow
D. a plant; cytokinesis; cell plate
E. a plant; cytokinesis; division furrow
D
In the diplontic life cycle diagram (shown) depicting stages of sexual reproduction, which stage (1–4) represents an adult elephant?
A. 1
B. 2
C. 3
D. 4
E. None of the above
D
This photomicrograph shows a human somatic cell containing 23 pairs of homologous chromosomes. Which of the following statements regarding homologous chromosomes is false?
A. Haploid cells have only one homolog from each of the pairs of homologous chromosomes.
B. Each of the homologs of a pair of chromosomes comes from a different parent.
C. There is a simple relationship between the number of pairs of homologous and the complexity of organisms.
D. Homologs of a pair of homologous chromosomes contain the same types of genetic information.
E. The size and appearance of a condensed homologous pair of chromosomes is generally the same.
C
Which of the following statements regarding meiosis I (shown here) is false?
A. Pairing of homologous chromosomes occurs along their entire length.
B. Meiosis I involves the separation of chromosomes into daughter cells.
C. Synapsis occurs during meiosis I.
D. The alignment of homologous chromosomes at the equatorial plate is random.
E. Paired homologous chromosomes are called tetrads.
B
Which of the following statements regarding crossing over (shown) is false?
A. Chiasmata are formed at areas of attachment between homologous chromosomes.
B. Crossing over occurs at areas where chiasmata appear between homologous chromosomes.
C. Crossing over increases genetic variation.
D. Recombinant chromatids result from crossing over.
E. Crossing over occurs during anaphase I of meiosis.
E
Which of the following statements about cell death is false?
A. Cell death by necrosis is highly specific.
B. Signal transduction pathways for apoptosis are similar in plants and animals.
C. Enzymes called “caspases” are made by cells entering apoptosis.
D. Apoptosis occurs during development.
E. Exposure of epithelial cells to radiation can induce apoptosis.
A
Treatments for cancer include radiation that damages _______, causing apoptosis, and 5-fluorouracil that blocks _______. Some agents, such as taxol, interfere with the formation of the _______.
A. proteins; DNA replication; mitotic spindle
B. DNA; protein synthesis; mitotic spindle
C. DNA; DNA replication; microfilaments
D. DNA; DNA replication; mitotic spindle
E. proteins; protein synthesis; microfilaments
D
