Chapter 9+10 Test

Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol disrupts microtubule formation by binding to microtubules and accelerating their assembly from the protein precursor, tubulin. Surprisingly, this stops mitosis. Specifically, Taxol must affect A) the formation of the mitotic spindle. B) anaphase. C) formation of the centrioles. D) chromatid assembly. E) the S phase of the cell cycle.

You have the technology necessary to measure each of the following in a sample of animal cells: chlorophylls, organelle density, picograms of DNA, cell wall components, and enzymatic activity. Which would you expect to increase significantly from M to G₁? A) organelle density and enzymatic activity B) cell wall components and DNA C) chlorophyll and cell walls D) organelle density and cell walls E) chlorophyll and DNA

Which of the following is true concerning cancer cells? A) They do not exhibit density-dependent inhibition when growing in culture. B) When they stop dividing, they do so at random points in the cell cycle. C) They are not subject to cell cycle controls. D) When they stop dividing, they do so at random points in the cell cycle, and they are not subject to cell cycle controls. E) When they stop dividing, they do so at random points in the cell cycle; they are not subject to cell cycle controls; and they do not exhibit density-dependent inhibition when growing in culture.

A research team began a study of a cultured cell line. Their preliminary observations showed them that the cell line did not exhibit either density-dependent inhibition or anchorage dependence. What could they conclude right away? A) The cells originated in the nervous system. B) The cells are unable to form spindle microtubules. C) They have altered series of cell cycle phases. D) The cells show characteristics of tumors. E) They were originally derived from an elderly organism.

The drug cytochalasin B blocks the function of actin. Which of the following aspects of the cell cycle would be most disrupted by cytochalasin B? A) spindle formation B) spindle attachment to kinetochores C) DNA synthesis D) cell elongation during anaphase E) cleavage furrow formation and cytokinesis

Which of the following does not occur during mitosis? A) condensation of the chromosomes B) replication of the DNA C) separation of sister chromatids D) spindle formation E) separation of the spindle poles

A human cell containing 22 autosomes and a Y chromosome is A) a sperm. B) an egg. C) a zygote. D) a somatic cell of a male. E) a somatic cell of a female.

Movement of the chromosomes during anaphase would be most affected by a drug that A) reduces cyclin concentrations. B) increases cyclin concentrations. C) prevents elongation of microtubules. D) prevents shortening of microtubules. E) prevents attachment of the microtubules to the kinetochore.

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

The karyotype of one species of primate has 48 chromosomes. In a particular female, cell division goes awry and she produces one of her eggs with an extra chromosome (25). The most probable source of this error would be a mistake in which of the following? A) mitosis in her ovary B) metaphase I of one meiotic event C) telophase II of one meiotic event D) telophase I of one meiotic event E) either anaphase I or II

Chromatids are separated from each other. A) The statement is true for mitosis only. B) The statement is true for meiosis I only. C) The statement is true for meiosis II only. D) The statement is true for mitosis and meiosis I. E) The statement is true for mitosis and meiosis II.

The centromere is a region in which A) chromatids remain attached to one another until anaphase. B) metaphase chromosomes become aligned at the metaphase plate. C) chromosomes are grouped during telophase. D) the nucleus is located prior to mitosis. E) new spindle microtubules form at either end.

For anaphase to begin, which of the following must occur? A) Chromatids must lose their kinetochores. B) Cohesin must attach the sister chromatids to each other. C) Cohesin must be cleaved enzymatically. D) Kinetochores must attach to the metaphase plate. E) Spindle microtubules must begin to depolymerize.

You have the technology necessary to measure each of the following in a sample of animal cells: chlorophylls, organelle density, picograms of DNA, cell wall components, and enzymatic activity. Which would you expect to increase significantly from M to G₁? A) organelle density and enzymatic activity B) cell wall components and DNA C) chlorophyll and cell walls D) organelle density and cell walls E) chlorophyll and DNA

During which phase of mitosis do the chromatids become chromosomes? A) telophase B) anaphase C) prophase D) metaphase E) cytokinesis

Which of the following triggers the cell's passage past the G₂ checkpoint into mitosis? A) PDGF B) MPF C) protein kinase D) cyclin E) Cdk

The cyclin component of MPF is destroyed toward the end of which phase? A) G₀ B) G₁ C) S D) G₂ E) M

A mutation results in a cell that no longer produces a normal protein kinase for the M phase checkpoint. Which of the following would likely be the immediate result of this mutation? A) The cell would prematurely enter anaphase. B) The cell would never leave metaphase. C) The cell would never enter metaphase. D) The cell would never enter prophase. E) The cell would undergo normal mitosis, but fail to enter the next G₁ phase.

Which of the following describe(s) cyclin-dependent kinase (Cdk)? A) Cdk is inactive, or "turned off," in the presence of cyclin. B) Cdk is present throughout the cell cycle. C) Cdk is an enzyme that attaches phosphate groups to other proteins. D) Cdk is inactive, or "turned off," in the presence of cyclin and it is present throughout the cell cycle. E) Cdk is present throughout the cell cycle and is an enzyme that attaches phosphate groups to other proteins.

A particular cyclin called cyclin E forms a complex with Cdk 2 (cyclin-dependent kinase 2). This complex is important for the progression of the cell from G₁ into the S phase of the cell cycle. Which of the following statements is correct? A) The amount of free cyclin E is greatest during the S phase. B) The amount of free Cdk 2 is greater during G₁ compared to the S phase. C) The amount of free cyclin E is highest during G₁. D) The amount of free Cdk 2 is greatest during G₁. E) The activity of the cyclin E/Cdk 2 complex is highest during G₂.

Which of the following most accurately describes a cyclin? A) It is present in similar concentrations throughout the cell cycle. B) It is activated to phosphorylate by complexing with a Cdk. C) It decreases in concentration when MPF activity increases. D) It activates a Cdk molecule when it is in sufficient concentration. E) It activates a Cdk when its concentration is decreased.

All cell cycle checkpoints are similar in which way? A) They respond to the same cyclins. B) They utilize the same Cdks. C) They give the go-ahead signal to progress to the next checkpoint. D) They each have only one cyclin/Cdk complex. E) They activate or inactivate other proteins.

Density-dependent inhibition is explained by which of the following? A) As cells become more numerous, they begin to squeeze against each other, restricting their size and ability to produce control factors. B) As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells and they stop dividing. C) As cells become more numerous, the protein kinases they produce begin to compete with each other, such that the proteins produced by one cell essentially cancel those produced by its neighbor. D) As cells become more numerous, more and more of them enter the S phase of the cell cycle. E) As cells become more numerous, the level of waste products increases, eventually slowing down metabolism.

Why do neurons and some other specialized cells divide infrequently? A) They no longer have active nuclei. B) They no longer carry receptors for signal molecules. C) They have been shunted into G₀. D) They can no longer bind Cdk to cyclin. E) They show a drop in MPF concentration.

What is a cleavage furrow? A) a ring of vesicles forming a cell plate B) the separation of divided prokaryotes C) a groove in the plasma membrane between daughter nuclei D) the metaphase plate where chromosomes attach to the spindle E) the space that is created between two chromatids during anaphase

Which of the following best describes how chromosomes move toward the poles of the spindle during mitosis? A) The chromosomes are "reeled in" by the contraction of spindle microtubules. B) Motor proteins of the kinetochores move the chromosomes along the spindle microtubules. C) Nonkinetochore spindle fibers serve to push chromosomes in the direction of the poles. D) The chromosomes are "reeled in" by the contraction of spindle microtubules, and motor proteins of the kinetochores move the chromosomes along the spindle microtubules. E) The chromosomes are "reeled in" by the contraction of spindle microtubules, motor proteins of the kinetochores move the chromosomes along the spindle microtubules, and nonkinetochore spindle fibers serve to push chromosomes in the direction of the poles.

Cells from an advanced malignant tumor most often have very abnormal chromosomes, and often an abnormal total number of chromosomes. Why might this occur? A) Cancer cells are no longer density dependent. B) Cancer cells are no longer anchorage dependent. C) Chromosomally abnormal cells can still go through cell cycle checkpoints. D) Chromosomally abnormal cells still have normal metabolism. E) Transformation introduces new chromosomes into cells.

The human genome is minimally contained in which of the following? A) every human cell B) each human chromosome C) the entire DNA of a single human D) the entire human population E) each human gene

Which of the following defines a genome? A) representation of a complete set of a cell's polypeptides B) the complete set of an organism's polypeptides C) the complete set of a species' polypeptides D) a karyotype E) the complete set of an organism's genes

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 per cell. B) The species has 16 sets of chromosomes per cell. C) Each cell has eight homologous pairs. D) During the S phase of the cell cycle there will be 32 separate chromosomes. E) A gamete from this species has four chromosomes.

At which stage of mitosis are chromosomes usually photographed in the preparation of a karyotype? A) prophase B) metaphase C) anaphase D) telophase E) interphase

A karyotype results from which of the following? A) a natural cellular arrangement of chromosomes in the nucleus B) an inherited ability of chromosomes to arrange themselves C) the ordering of human chromosome images D) the cutting and pasting of parts of chromosomes to form the standard array E) the separation of homologous chromosomes at metaphase I of meiosis

Which of the following best describes a karyotype? A) a pictorial representation of all the genes for a species B) a display of each of the chromosomes of a single cell C) the combination of all the maternal and paternal chromosomes of a species D) the collection of all the chromosomes in an individual organism E) a photograph of all the cells with missing or extra chromosomes

A given organism has 46 chromosomes in its karyotype. We can therefore conclude which of the following? A) It must be human. B) It must be a primate. C) It must be an animal. D) It must be sexually reproducing. E) Its gametes must have 23 chromosomes.

How does the sexual life cycle increase the genetic variation in a species? A) by allowing crossing over B) by allowing fertilization C) by increasing gene stability D) by conserving chromosomal gene order E) by decreasing mutation frequency

Which of the following best describes the frequency of crossing over in mammals? A) ~50 per chromosome pair B) ~2 per meiotic cell C) at least 1-2 per chromosome pair D) ~1 per pair of sister chromatids E) a very rare event among hundreds of cells

There is a group of invertebrate animals called rotifers, among which a particular group of species reproduces, as far as is known, only asexually. These rotifers, however, have survived a long evolutionary history without evidence of having been overcome by excessive mutations. 61) Assuming that the eggs are diploid, tetraploid, or partially tetraploid, what mechanism may still occur without fertilization? A) meiosis in each generation B) meiosis in every second generation C) independent assortment of maternal and paternal chromosomes D) meiosis in times of adverse environmental conditions E) crossing over of homologs

Which of the following might result in a human zygote with 45 chromosomes? A) an error in either egg or sperm meiotic anaphase B) failure of the egg nucleus to be fertilized by the sperm C) fertilization of a 23 chromosome human egg by a 22 chromosome sperm of a closely related species D) an error in the alignment of chromosomes on the metaphase plate E) lack of chiasmata in prophase I

Chromatids are separated from each other. A) The statement is true for mitosis only. B) The statement is true for meiosis I only. C) The statement is true for meiosis II only. D) The statement is true for mitosis and meiosis I. E) The statement is true for mitosis and meiosis II.

To visualize and identify meiotic cells at metaphase with a microscope, what would you look for? A) sister chromatids grouped at the poles B) individual chromosomes all at the cell's center C) an uninterrupted spindle array D) the synaptonemal complex E) tetrads all aligned at the cell's center

For a species with a haploid number of 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes? A) 23 B) 46 C) 460 D) 920 E) about 8 million

Independent assortment of chromosomes is a result of A) the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I. B) the random nature of the fertilization of ova by sperm. C) the random distribution of the sister chromatids to the two daughter cells during anaphase II. D) the relatively small degree of homology shared by the X and Y chromosomes. E) the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I, the random nature of the fertilization of ova by sperm, the random distribution of the sister chromatids to the two daughter cells during anaphase II, and the relatively small degree of homology shared by the X and Y chromosomes.

How is natural selection related to sexual reproduction as opposed to asexual reproduction? A) Sexual reproduction results in many new gene combinations, some of which will lead to differential reproduction. B) Sexual reproduction results in the most appropriate and healthiest balance of two sexes in the population. C) Sexual reproduction results in the greatest number of new mutations. D) Sexual reproduction allows the greatest number of offspring to be produced. E) Sexual reproduction utilizes far less energy than asexual reproduction.