PT: Chapter 9- The Cell Cycle

Assume that you are dealing with a species that has 14 chromosomes per somatic cell. How many sister chromatids are present in early telophase of mitosis? (Section 9.2) A. 0 B. 7 C. 14 D. 28 E. None of the choices is correct.

A. 0 feedback: In this case, mitosis starts with 14 chromosomes, each of which consists of two chromatids, because the cell has been through the S phase. By telophase, the chromatids have separated and the individual units of DNA (now called chromosomes) are arriving at the poles. There are no chromatids at this point.

How many maternal chromosomes are present in a somatic human cell not engaged in cell division? (Section 9.1) A. 23 B. 46 C. 92 D. 184 E. None of the choices is correct.

A. 23 feedback: Human somatic cells (all the body cells except the reproductive cells) contain a total of 46 chromosomes, half of which are maternally derived, and the other half paternally derived.

Which is involved in the binary fission of bacteria? (Section 9.2) A. distribution of a copy of the single parental chromosome to each daughter cell B. formation of a spindle apparatus C. disintegration of the nuclear membrane D. prophase, prometaphase, metaphase, anaphase, and telophase E. formation of a cell plate

A. distribution of a copy of the single parental chromosome to each daughter cell feedback: Prokaryotes reproduce by a type of cell division called binary fission, which involves replicating the single chromosome and distributing the copies equally to two daughter cells.

At which stage of mitosis are chromosomes lined up in one plane in preparation for their separation to opposite poles of the cell? (Section 9.2) A. metaphase B. interphase C. telophase D. anaphase E. prophase

A. metaphase feedback: The chromosomes convene on the metaphase plate, an imaginary plane that is equidistant from the spindle's two poles.

Which process does not occur in dividing bacteria? (Section 9.2) A. mitosis B. inward growth of the plasma membrane C. replication of DNA D. binary fission E. separation of the origins of replication

A. mitosis feedback: Mitosis does not occur in dividing bacteria. Mitosis might have had its origins in simpler bacterial mechanisms of cell reproduction. Prokaryotes (bacteria) reproduce by a type of cell division called binary fission.

Which phase of mitosis is essentially the opposite of prometaphase in terms of the nuclear envelope? (Section 9.2) A. telophase B. S phase C. metaphase D. anaphase E. interphase

A. telophase feedback: In prometaphase, the nuclear envelope fragments and the kinetochores attach to microtubules. During telophase, fragments of the nuclear envelope begin to reassemble along with portions of the endomembrane system.

A cell biologist carefully measured the quantity of DNA in grasshopper cells growing in cell culture. Cells examined during the G2 phase of the cell cycle contained 200 units of DNA. What would be the amount of DNA at G1 of the cell cycle in one of the grasshopper daughter cells? (Section 9.2) A. 50 units B. 100 units C. between 50 and 100 units D. 200 units E. 400 units

B. 100 units feedback: Recall that G2follows S and that during the S phase of interphase in the cell cycle, DNA is replicated.

If a cell contains 60 chromatids at the start of mitosis, how many chromosomes will be found in each daughter cell at the completion of the cell cycle? (Section 9.2) A. 15 B. 30 C. 45 D. 60 E. 120

B. 30 feedback: In this case, mitosis starts with 30 chromosomes, each of which consists of two chromatids. At the completion of mitosis, each daughter cell will contain 30 chromosomes, each of which had been one chromatid at the start of the process.

When a cell in S phase is fused with a cell in G1, __________. (Section 9.3) A. the chromosomes of the original G1 nucleus condense in preparation for mitosis B. DNA synthesis begins immediately in the original G1nucleus C. the original G1 cell will divide immediately D. the replication of DNA occurring in the original S nucleus is terminated E. the two nuclei fuse and further division is arrested

B. DNA synthesis begins immediately in the original G1nucleus feedback: This observation indicates that cytoplasmic signals can participate in the regulation of the cell cycle.

The complex of DNA and protein that makes up a eukaryotic chromosome is properly called __________. (Section 9.1) A. a chromatid B. chromatin C. a centrosome D. a chromoplast E. a centromere

B. chromatin feedback: The DNA-protein complex called chromatin is organized into a long, thin fiber.

In animal cell mitosis, the cleavage furrow forms during which stage of the cell cycle? (Section 9.2) A. the G1 phase B. cytokinesis C. prophase D. anaphase E. metaphase

B. cytokinesis feedback: Cytokinesis is often underway by telophase. In animal cells, cytokinesis involves the formation of a cleavage furrow, which pinches the cell in two.

During interphase, the genetic material of a typical eukaryotic cell is __________. (Section 9.2) A. condensed and the chromosomes are often visible under the light microscope B. dispersed in the nucleus as long strands of chromatin C. dispersed in the cytoplasm as long strands of chromatin D. attached to microtubule spindle fibers E. transported through the nuclear pores

B. dispersed in the nucleus as long strands of chromatin feedback: During interphase, the chromosomes cannot be distinguished individually because they are still in the form of loosely packed chromatin fibers.

Observations of cancer cells in culture support the hypothesis that cancer cells __________. (Section 9.3) A. produce molecules that inhibit the growth factors required for cell division B. do not exhibit density-dependent inhibition C. exhibit anchorage dependence D. spend the majority of their time in the G0 phase E. All of the listed responses are correct.

B. do not exhibit density-dependent inhibition feedback: Normal cells respond to density-dependent inhibition by growing in culture to form a single layer of cells.

Chromatids are __________. (Section 9.1) A. the bacterial equivalent of eukaryotic chromosomes B. identical copies of each other if they are part of the same chromosome C. held together by the centrioles D. found only in aberrant chromosomes E. composed of RNA

B. identical copies of each other if they are part of the same chromosome feedback: Each duplicated chromosome consists of two identical sister chromatids.

Which represents an incorrect description? (Section 9.2) A. telophase: chromosomes become more extended B. metaphase: the nuclear envelope disappears C. metaphase: chromosomes line up on the equatorial plane D. anaphase: there is movement of the chromosomes to the poles E. prophase: chromosomes become more tightly coiled right answer

B. metaphase: the nuclear envelope disappears feedback: During prometaphase, the nuclear envelope fragments.

One event occurring during prophase is __________. (Section 9.2) A. the alignment of chromosomes in a single plane B. the beginning of the formation of a spindle apparatus C. the synthesis of a new nuclear envelope D. cytokinesis E. division of the centromere

B. the beginning of the formation of a spindle apparatus feedback: During prophase, the mitotic spindle begins to form.

The function of the cell cycle is to produce daughter cells that __________. (Section 9.1) A. have the same number of chromatids as the parent cell had chromosomes B. have a random assortment of maternal and paternal chromosomes C. are genetically identical to the parent cell (assuming no mutation has occurred) D. have the same number of chromosomes as the parent cell but not the same genetic content E. None of the choices is correct.

C. are genetically identical to the parent cell (assuming no mutation has occurred) feedback: Cell division involves the distribution of identical genetic material (DNA) to two daughter chromosomes.

A biochemist measured the amount of DNA in cells growing in the laboratory and found that the quantity of DNA in the cells doubled __________. (Section 9.2) A. between prophase and anaphase of mitosis B. during the M phase of the cell cycle C. between the G1 and G2 phases of interphase D. between anaphase and telophase of mitosis E. between the G2 phase and prophase

C. between the G1 and G2 phases of interphase feedback: Between these two phases of the cell cycle, the DNA is replicated during the S phase.

Tissue culture experiments with PDGF demonstrate that without this substance __________. (Section 9.3) A. cells divide in an uncontrolled fashion, confirming PDGF's role as a cell division inhibitor B. the various kinases, such as MPF, are unable to bind to cyclin C. fibroblasts fail to divide D. animal cells are unable to attach to the substratum E. bacterial cells lose their resistance to antibiotics

C. fibroblasts fail to divide feedback: PDGF is a specific growth factor for fibroblasts.

You would be unlikely to see which human cell dividing? (Section 9.3) A. cell from an embryo B. intestinal lining cell C. nerve cell D. cancer cell E. skin cell

C. nerve cell feedback: Nerve cells are quite complex and specialized. After reaching maturity, they enter the G0phase.

DNA replication occurs in __________. (Section 9.2) A. the G1 phase of interphase in reproductive cells only B. the cytokinesis portion of the cell's life cycle C. the S phase of interphase in both somatic and reproductive cells D. prophase of both mitosis and meiosis E. metaphase of meiosis only

C. the S phase of interphase in both somatic and reproductive cells feedback: Chromosomes are duplicated only during the S phase ("S" stands for the synthesis of DNA).

Following cytokinesis in an animal cell, how many centrioles does each new daughter cell possess? (Section 9.2) A. zero B. one C. two D. four E. eight

C. two feedback: Each daughter cell inherits a single centrosome following cytokinesis and each centrosome contains two centrioles.

If a normal somatic human cell is just about to divide, it has __________ chromatids. (Section 9.2) A. 0 B. 23 C. 46 D. 92 E. There is not enough information to answer the question.

D. 92 feedback: Remember normal human cells have 46 chromosomes or 23 pairs. So human somatic cells will have 92 chromatids just prior to cell division due to the replication of DNA that occurs in the S phase.

Down syndrome is characterized by cells having three copies of chromosome 21. As a cell in an individual with Down syndrome prepares to enter mitosis, how many chromatids would be present? (Section 9.2) A. 23 B. 46 C. 92 D. 94 E. 98

D. 94 feedback: Cells from an individual with Down syndrome would have 23 pairs of chromosomes, plus an extra chromosome at 21 for a total of 47. This is called trisomy because there is an extra chromosome at 21. At the S phase, those chromosomes replicate to produce 94 sister chromatids.

During which phase in the cell cycle would you find the most DNA per cell? (Section 9.2) A. G1 B. S1 C. S D. G2 E. prophase II

D. G2 feedback: Chromosomes are duplicated only during the S phase ("S" stands for the synthesis of DNA) of interphase. The phase following completion of the S phase is G2of interphase.

The person credited with first recognizing (in the 1850s) that living cells cannot arise spontaneously, but arise only from previously existing cells, is __________. (Section 9.1) A. Louis Pasteur B. Robert Hooke C. Watson D. Rudolf Virchow E. Anton van Leeuwenhoek

D. Rudolf Virchow feedback: In 1855 Rudolf Virchow stated, "Where a cell exists, there must have been a preexisting cell."

In telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in __________. (Section 9.2) A. interphase B. metaphase C. anaphase D. prophase E. S phase

D. prophase feedback: During prophase, we observe the formation of the spindle fibers, the condensation of chromatin, and the disappearance of the nucleolus.

In a human skin cell that is going through the cell cycle, when do the centrosomes separate? (Section 9.2) A. S phase B. G2 phase C. metaphase D. prophase E. anaphase

D. prophase feedback: The centrosomes move away from each other during prophase, apparently propelled along the surface of the nucleus by the lengthening bundles of microtubules between them.

What is the difference between a benign tumor and a malignant tumor? (Section 9.3) A. Benign tumors arise by transformation; malignant tumors do not. B. Benign tumors do not arise by transformation; malignant tumors do. C. Benign tumors will not kill you; malignant tumors will. D. Cells of benign tumors metastasize; those of malignant tumors do not. E. Cells of benign tumors do not metastasize; those of malignant tumors do.

E. Cells of benign tumors do not metastasize; those of malignant tumors do. feedback: Cells of malignant tumors spread from their site of origin to other parts of the body.

A cell entering the cell cycle with 32 chromosomes will produce two daughter cells, each with __________. (Section 9.1) A. 32 pairs of chromosomes B. 64 chromosomes C. 16 chromosomes D. 64 pairs of chromosomes E. None of the choices is correct.

E. None of the choices is correct. feedback:There would be 32 chromosomes present in each of the daughter cells.

Cytokinesis refers to __________. (Section 9.1) A. reduction in the number of chromosomes B. movement of a cell from one place to another C. division of the entire cell D. division of the nucleus E. division of the cytoplasm

E. division of the cytoplasm feedback: Cytokinesis is the division of the cytoplasm that follows the mitotic division of the nucleus.

You would know a dividing cell was a plant cell rather than an animal cell if you saw that __________. (Section 9.2) A. the nucleolus was visible during metaphase B. it had formed a cleavage furrow C. it had microtubules D. it had two pairs of centrioles during prophase E. it had formed a cell plate

E. it had formed a cell plate feedback: The cell plate, which divides the cytoplasm in two, forms during the telophase of mitosis in a plant cell.

Which of the following does not occur during mitosis? (Section 9.2) A. separation of chromatids B. alignment of chromosomes along the cell's equator C. condensation of chromatin D. the movement of chromosomes to opposite poles E. replication of chromosomes feedback: The DNA of the chromosomes is replicated in the S phase of interphase before mitosis.

E. replication of chromosomes feedback: The DNA of the chromosomes is replicated in the S phase of interphase before mitosis.

During binary fission in a bacterium __________. (Section 9.2) A. the two DNA molecules attach to the centrioles B. the two DNA molecules float free in the cell and are guided to daughter cells by a spindle-like apparatus C. the two DNA molecules break up into plasmids D. the two DNA molecules divide in half, forming four DNA fragments E. the origins of replication move apart

E. the origins of replication move apart feedback:This occurs during binary fission.