Mastering Bio

Question 1

Which event does not take place before the start of mitosis? *Organelles proliferate. *The nuclear envelope disintegrates. *DNA is replicated. *The parent cell grows.

Answer 1

The nuclear envelope disintegrates.

Question 2

True or false? Mitosis takes place during M phase, which is the longest phase of the cell cycle.

Answer 2

False

Question 3

Which term describes two recently replicated DNA strands that are joined together just before cell division?

Answer 3

Sister chromatids

Question 4

During which stage of mitosis are chromosomes lined up in the center of the cell?

Answer 4

Metaphase

Question 5

Which stage of mitosis is characterized by the disintegration of mitotic spindles and the formation of two new nuclear membranes?

Answer 5

Telophase

Question 6

To which part of the centromere do mitotic spindle fibers attach during prometaphase?

Answer 6

Kinetochore

Question 7

During which substage of mitosis do sister chromatids break apart and start moving to opposite poles of the cell?

Answer 7

Anaphase

Question 8

Which term describes centromeres uncoupling, sister chromatids separating, and the two new chromosomes moving to opposite poles of the cell?

Answer 8

anaphase

Question 9

A cell containing 92 chromatids at metaphase of mitosis would, at its completion, produce two nuclei each containing how many chromosomes?

Answer 9

46

Question 10

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. Those cells would have __________ picograms at the end of the S phase and __________ picograms at the end of G2.

Answer 10

16; 16

Question 11

Why do chromosomes coil during mitosis?

Answer 11

to allow the chromosomes to move without becoming entangled and breaking

Question 12

G1 is represented by which number(s)?

Answer 12

I and IV

Question 13

Cells that are in a nondividing state are in which phase?

Answer 13

G0

Question 14

Which is a general term for enzymes that activate or inactivate other proteins by phosphorylating them?

Answer 14

protein kinase

Question 15

Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to

Answer 15

disruption of mitotic spindle formation.

Question 16

Which of the following is a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically active?

Answer 16

Cdk

Question 17

A particular cyclin called cyclin E forms a complex with a cyclin-dependent kinase called Cdk 2. This complex is important for the progression of the cell from G 1 into the S phase of the cell cycle. Which of the following statements is correct? *The amount of Cdk 2 is greater during G 1 compared to the S phase. *The amount of Cdk 2 is greatest during G 1 . *The amount of cyclin E is highest during G 1 . * The amount of cyclin E is greatest during the S phase. *The activity of the cyclin E/Cdk 2 complex is highest during G 2 .

Answer 17

The amount of cyclin E is highest during G1.

Question 18

Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor?

Answer 18

lack of appropriate cell death

Question 19

Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have times more DNA than G1 phase cells. The cells of this group are _____.

Answer 19

in the S phase of the cell cycle

Question 20

A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain?

Answer 20

92

Question 21

Why is it difficult to observe individual chromosomes with a light microscope during interphase?

Answer 21

They have uncoiled to form long, thin strands.

Question 22

What is true of benign tumors, but not malignant tumors?

Answer 22

They remain confined to their original site

Question 23

Neurons and some other specialized cells divide infrequently because they _____.

Answer 23

have entered into G0

Question 24

Cyclin-dependent kinase (Cdk) is _____.

Answer 24

an enzyme that attaches phosphate groups to other proteins

Question 25

Which of the following is a protein synthesized at specific times during the cell cycle that associates with a kinase to form a catalytically active complex? \*Cdk \*MPF \*PDGF \*cyclin

Answer 25

cyclin

Question 26

Which of the following is a protein maintained at steady levels throughout the cell cycle that requires cyclin to become catalytically active? \*PDGF \*MPF \*cyclin \*Cdk

Answer 26

Cdk

Question 27

In the figure, MPF reaches its highest concentration during this stage.

Answer 27

III

Question 28

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?

Answer 28

The cells show characteristics of tumors.

Question 29

For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable? \*It interferes with rapidly dividing cells. \*It does not alter metabolically active cells. \*It is safe enough to limit all apoptosis. \*It interferes with cells entering G 0 .

Answer 29

It interferes with rapidly dividing cells.

Question 30

Cells from advanced malignant tumors often have very abnormal chromosomes and an abnormal number of chromosomes. What might explain the association between malignant tumors and chromosomal abnormalities?

Answer 30

Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities.

Question 31

What is the final result of mitosis in a human?

Answer 31

genetically identical somatic cells containing 46 chromosomes

Question 32

If there are 20 duplicated chromosomes in a cell, how many centromeres are there?

Answer 32

20

Question 33

True statement about kinetochores?

Answer 33

They are sites at which microtubules attach to chromosomes.

Question 34

Which of the following correctly matches a phase of the cell cycle with its description? \*G 1 : follows cell division \*M: duplication of DNA \*S: immediately precedes cell division \*G 2 : cell division \*All of the above are correctly matched.

Answer 34

G1: follows cell division

Question 35

In some organisms, such as certain fungi and algae, cells undergo the cell cycle repeatedly without subsequently undergoing cytokinesis. What would result from this?

Answer 35

large cells containing many nuclei

Question 36

Cytochalasin B is a chemical that disrupts microfilament formation. How would this interfere with cell division?

Answer 36

cleavage

Question 37

In human and many other eukaryotic species' cells, the nuclear membrane has to disappear to permit \_\_\_\_\_.

Answer 37

the attachment of microtubules to kinetochores

Question 38

At which phase are centrioles beginning to move apart in animal cells?

Answer 38

prophase

Question 39

Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol disrupts microtubule formation. Surprisingly, this stops mitosis. Specifically, Taxol must affect \_\_\_\_\_.

Answer 39

the structure of the mitotic spindle

Question 40

Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per nucleus. In which stage of the cell cycle did the nucleus contain 6 picograms of DNA?

Answer 40

G2

Question 41

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms would be found at the end of S and the end of G2?

Answer 41

16; 16

Question 42

The beginning of anaphase is indicated by which of the following? \*Chromatids lose their kinetochores. \*Spindle microtubules begin to polymerize. \*Cohesin is cleaved enzymatically. \*Cohesin attaches the sister chromatids to each other.

Answer 42

Cohesin is cleaved enzymatically.

Question 43

During which phase of mitosis do the chromatids become chromosomes?

Answer 43

anaphase

Question 44

What is the correct chromosomal condition at prometaphase of mitosis?

Answer 44

B

Question 45

What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis?

Answer 45

E

Question 46

If the cell whose nuclear material is shown in the accompanying figure continues toward completion of mitosis, which of the following events would occur next?

Answer 46

formation of telophase nuclei

Question 47

In the figure, which number represents DNA synthesis?

Answer 47

II

Question 48

In the figure, at which of the numbered regions would you expect to find cells at metaphase?

Answer 48

III only

Question 49

Centromeres split and sister chromatids migrate to opposite poles in meiosis \_\_\_\_\_.

Answer 49

anaphase II

Question 50

The DNA content of a diploid cell in the G1 phase of the cell cycle is x. The DNA content of a single cell at metaphase of meiosis II would be

Answer 50

x

Question 51

Homologous pairs of chromosomes align opposite of each other at the equator of a cell during \_\_\_\_\_.

Answer 51

meiosis metaphase I

Question 52

Which diagram represents anaphase I of meiosis?

Answer 52

I

Question 53

When we first see chiasmata under a microscope, we know that \_\_\_\_\_.

Answer 53

prophase I is occurring

Question 54

After telophase I of meiosis, the chromosomal makeup of each daughter cell is \_\_\_\_\_.

Answer 54

haploid, and the chromosomes are each composed of two chromatids

Question 55

What is crossing over?

Answer 55

the exchange of homologous portions of nonsister chromatids

Question 56

What is karyotype?

Answer 56

organized images of a cells chromosomes

Question 57

Quaking aspen can send out underground stems for asexual reproduction. Sexual reproduction is not as common, but when it does happen, the haploid gametes have 19 chromosomes. How many chromosomes are in the cells of the underground stems?

Answer 57

38

Question 58

If meiosis produces haploid cells, how is the diploid number restored for those organisms that spend most of their life cycle in the diploid state?

Answer 58

fertilization

Question 59

In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, what do the two chromosomes of the pair have in common?

Answer 59

length, centromere position, staining pattern, and traits coded for by their genes

Question 60

A triploid cell contains sets of three homologous chromosomes. If a cell of a usually diploid species with 42 chromosomes per cell is triploid, this cell would be expected to have which of the following? \*21 chromosome pairs and 21 unique chromosomes \*63 chromosomes in pairs \*63 chromosomes, each with three chromatids \*63 chromosomes in 21 sets of 3

Answer 60

63 chromosomes in 21 sets of 3

Question 61

Which of the following is true of a species that has a chromosome number of 2 n = 16? \*A gamete from this species has four chromosomes. \*Each diploid cell has eight homologous pairs. \*The species is diploid with 32 chromosomes per cell. \*The species has 16 sets of chromosomes per cell.

Answer 61

Each diploid cell has eight homologous pairs.

Question 62

How are sister chromatids and homologous chromosomes different from each other?

Answer 62

Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication.

Question 63

Define a genome

Answer 63

the complete set of an organism's genes and other DNA sequences

Question 64

Which of the following occurs during meiosis but not during mitosis? \*Chromosomes migrate to opposite poles. \*Synapsis occurs. \*Chromosomes align at the metaphase plate. \*Chromosomes condense. \*A spindle apparatus forms.

Answer 64

Synapsis occurs

Question 65

Which of the life cycles is typical for animals?

Answer 65

I only

Question 66

A given organism has 23 pairs of homologs in its karyotype. Therefore, we can conclude that it must \_\_\_\_\_.

Answer 66

have gametes with 23 chromosomes

Question 67

If a cell has completed meiosis I and is just beginning meiosis II, which of the following is an appropriate description of its contents? \*It has half the chromosomes but twice the DNA of the originating cell. \*It has one-fourth the DNA and one-half the chromosomes as the originating cell. \*It has half the amount of DNA as the cell that began meiosis. \*It is identical in content to another cell formed from the same meiosis I event.

Answer 67

It has half the amount of DNA as the cell that began meiosis.

Question 68

What happens at the conclusion of meiosis 1?

Answer 68

Homologous chromosomes of a pair are separated from each other.

Question 69

Sister chromatids separate from each other during \_\_\_\_\_.

Answer 69

mitosis and meiosis II

Question 70

Which of the following occurs in meiosis but not in mitosis? \*alignment of chromosomes at the equator \*condensation of chromosomes \*chromosome replication \*synapsis of chromosomes

Answer 70

synapsis of chromosomes

Question 71

Which diagram represents anaphase II of meiosis?

Answer 71

V

Question 72

Which sample of DNA might be from a nerve cell arrested in G0 of the cell cycle?

Answer 72

I

Question 73

Which sample might represent an animal cell in the G2 phase of the cell cycle?

Answer 73

II

Question 74

Which sample might represent a zygote?

Answer 74

I

Question 75

What is a major difference between meiosis II and mitosis in animals?

Answer 75

Meiosis II occurs only in haploid cells, while mitosis occurs only in diploid cells.

Question 76

What is a major difference between mitosis and meiosis I in a diploid organism?

Answer 76

Sister chromatids separate in mitosis, while homologous pairs of chromosomes separate in meiosis I.

Question 77

Crossing over normally takes place during which of the following processes?

Answer 77

meiosis 1