[9] Mastering Biology

Question 1

Humans produce skin cells by mitosis and gametes by meiosis. Which of the following statements about the nuclei of skin cells is correct?

a) They contain the same amount of DNA as the nuclei of gametes produced by meiosis.
b) They contain four times as much DNA as the nuclei of gametes produced by meiosis.
c) They contain half as much DNA as the nuclei of gametes produced by meiosis.
d) They contain twice as much DNA as the nuclei of gametes produced by meiosis.

Answer 1

d) They contain twice as much DNA as the nuclei of gametes produced by meiosis.

Question 2

The beginning of anaphase is indicated by which of the following events?

Answer 2

enzymatic cleavage of cohesin

Question 3

Movement of the chromosomes during anaphase would be most affected by a drug that prevents which of the following processes?

Answer 3

shortening of microtubules

Question 4

Why do most cells in the human body divide infrequently?

Answer 4

They have exited the cell cycle and entered G0.

Question 5

Which of the following molecules or structures are primarily responsible for cytokinesis in plant cells but not in animal cells?

Answer 5

Golgi-derived vesicles

Question 6

Beginning with a fertilized egg (zygote), how many cells would be present in an embryo following a series of five cell divisions?

Answer 6

32

Question 7

The unlettered circle at the top of the figure above shows a diploid nucleus with four chromosomes that have not yet replicated. There are two pairs of homologous chromosomes, one long and the other short. One haploid set is black, and the other is gray. The circles labeled A−E show various combinations of these chromosomes. Which image displays the chromosomal composition of one daughter nucleus at telophase of mitosis?

Answer 7

E

Question 8

The unlettered circle at the top of the figure above shows a diploid nucleus with four chromosomes that have not yet replicated. There are two pairs of homologous chromosomes, one long and the other short. One haploid set is black, and the other is gray. The circles labeled A−E show various combinations of these chromosomes. What is the correct chromosomal condition for a nucleus at prophase of mitosis?

Answer 8

B

Question 9

The unlettered circle at the top of the figure above shows a diploid nucleus with four chromosomes that have not yet replicated. There are two pairs of homologous chromosomes, one long and the other short. One haploid set is black, and the other is gray. The circles labeled A−E show various combinations of these chromosomes. What is the correct chromosomal condition for a nucleus in G1 of the cell division cycle?

Answer 9

E

Question 10

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

a) alignment of chromosomes at the metaphase plate
b) synthesis of sister chromatids
c) cell membrane synthesis
d) segregation of daughter chromosomes toward the poles
e) formation of telophase nuclei

Answer 10

d) segregation of daughter chromosomes toward the poles

Question 11

Which of the following is true of kinetochores?

a) They are the primary centromere structures that maintain the attachment of the sister chromatids prior to mitosis.
b) They interdigitate at the cell’s equator and then move apart, causing the cell to elongate.
c) They attach to the ring of actin along the cytoplasmic surface of the plasma membrane, causing the actin to contract to form the cleavage furrow.
d) They are sites at which microtubules attach to chromosomes.
e) They are located at the center of the centrosome; their function is to organize tubulin into elongated bundles called spindle fibers.

Answer 11

d) They are sites at which microtubules attach to chromosomes.

Question 12

Where do the microtubules of the spindle originate during mitosis in animal cells?

Answer 12

centrosome

Question 13

At which phase of mitosis do the sister chromatids become daughter chromosomes?

Answer 13

anaphase

Question 14

What is a cleavage furrow?

Answer 14

a groove in the plasma membrane between daughter nuclei

Question 15

Where are the motor proteins that move chromosomes toward the poles of the mitotic spindle located?

Answer 15

on the kinetochores and at the centrosomes

Question 16

Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle?

Answer 16

G1

Question 17

Which of the following is true of benign tumors but not malignant tumors?

Answer 17

They remain confined to their original site.

Question 18

What will be the result if a eukaryotic cell completes mitosis but does not undergo cytokinesis?

Answer 18

one cell with two nuclei, each identical to the nucleus of the parent cell

Question 19

Which of the following components make(s) up eukaryotic chromatin?

Answer 19

DNA and proteins

Question 20

Somatic cells in elephants have 56 chromosomes. How many chromosomes would be carried by the gametes produced by elephants?

Answer 20

28

Question 21

Following DNA replication, each eukaryotic chromosome consists of two identical DNA molecules known as

Answer 21

sister chromatids

Question 22

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

Answer 22

92

Question 23

What is true of all cancers?

Answer 23

They have escaped normal cell cycle controls.

Question 24

DNA replication produces two identical DNA molecules, called _____, which separate during mitosis.

Answer 24

sister chromatid(s)

Question 25

After chromosomes condense, the _____ is the region where the identical DNA molecules are most tightly attached to each other.

Answer 25

centomere(s)

Question 26

3. During mitosis, microtubules attach to chromosomes at the ____.

Answer 26

kinetochore(s)

Question 27

4. In dividing cells, most of the cell’s growth occurs during _____.

Answer 27

interphase

Question 28

5. The _____ is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division.

Answer 28

mitotic spindles

Question 29

6. During interphase, most of the nucleus is filled with a complex of DNA and protein in a dispersed form called _____.

Answer 29

chromatin

Question 30

7. In most eukaryotes, division of the nucleus is followed by ______, when the rest of the cell divides.

Answer 30

cytokinesis

Question 31

8. The _____ are the organizing centers for microtubules involved in separating chromosomes during mitosis.

Answer 31

centrosomes