Chapter 12 - Cell Cycle

Question 1

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

Answer 1

92 chromatids

Question 2

A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing ( ) chromosomes.

Answer 2

16 chromosomes

Question 3

During ( ) both the contents of the nucleus and the cytoplasm are divided

Answer 3

The mitotic phase

Question 4

Nucleoli are present during ( )

Answer 4

Interphase

Question 5

Cytokinesis often, but not always, accompanies ( )

Answer 5

Telophase

Question 6

Chromosomes become visible during ( )

Answer 6

Prophase

Question 7

Centromeres divide and sister chromosomes become full fledge chromosomes during ( )

Answer 7

Anaphase

Question 8

Spindle fibers attach to kinetochores during

Answer 8

Prometaphase

Question 9

The person credited with first recognizing (in the 1860s) that living cells cannot arise spontaneously, but arise only from previously existing cells is ( ).

Answer 9

Rudolf Virchow

Question 10

Mitosis and cytokinesis result in the formation of ( ); meiosis and cytokinesis result in the formation of ( ).

Answer 10

2 diploid cells …. 4 haploid cells

Question 11

A human somatic cell contains ( ) chromosomes

Answer 11

46 chromosomes

Question 12

The function of the cell cycle is to produce daughter cells that ( ).

Answer 12

Are genetically identical to the parent cell (assuming no mutation has occurred)

Question 13

The region of a chromosome holding the 2 double strands of replicated DNA together is called ( ).

Answer 13

A centromere

Question 14

Chromatids are ( ).

Answer 14

Identical copies of each other if they are part of the same chromosome

Question 15

The centromere is a region in which ( ).

Answer 15

Chromatids are attached in prophase

Question 16

A biochemist measured the amount of DNA in cells growing in the laboratory and found that the quantity of DNA in a cell doubled ( ).

Answer 16

Between the G1 and G2 phases

Question 17

When a cell in S phase is fused with a cell in G1

Answer 17

DNA synthesis begins immediately in the original G1 nucleus

Question 18

DNA replication occurs ( ).

Answer 18

in the S phase of interphase in both somatic and reproductive cells

Question 19

chromatids form ( ).

Answer 19

during the S phase

Question 20

which of the following does Not occur during, or because of, mitosis?

a) chromosomes align along the cell’s equator
b) chromosomes replicate

Answer 20

b) chromosomes replicate

Question 21

how many chromosomes are present in a somatic human cell in G1

Answer 21

46 chromosomes

Question 22

if a somatic human cell is just about to divide, it has ( ) homologous pairs

Answer 22

23 homologous pairs

Question 23

which of the following phases of mitosis is essentially the opposite of prometaphase in terms of the nuclear envelope?

Answer 23

telophase

Question 24

in some organisms such as certain fungi and algae, cells undergo mitosis repeatedly without subsequently undergoing cytokinesis. What would result from this?

Answer 24

Large cells containing many nuclei

Question 25

Assume that you are dealing with a species in which the number of chromosomes in each somatic cell is 14. How many double-stranded chromosomes are present in the early telophase of mitosis/

Answer 25

0 double-stranded chromosomes

Question 26

At which point in the cell cycle do centrosomes begin to move apart to 2 poles of the cell in a dividing human liver cell?

Answer 26

Prophase

Question 27

The phase of mitosis during which the chromosomes move toward separate poles of the cell is ( ).

Answer 27

Anaphase

Question 28

One event occurring during prophase is ( ).

Answer 28

the beginning of the formation of a spindle apparatus

Question 29

Single sister chromatids are found in cells at mitotic ( ).

Answer 29

anaphase and telophase

Question 30

In animal cell mitosis, the cleavage furrow forms during

Answer 30

Cytokinesis

Question 31

At which stage of mitosis are chromosomes lined up in one plane in preparation for their separation to opposite poles of the cell?

Answer 31

Metaphase

Question 32

The term "binary fission" is best applied to ( ).

Answer 32

Prokaryotes

Question 33

During binary fission in a bacterium ( ).

Answer 33

The origins of replication move apart

Question 34

Do prokaryotic cells undergo mitotic division?

Answer 34

No, never

Question 35

Binary fission in bacterial cells involves ( ).

Answer 35

Distribution of a copy of the single parental chromosome to each daughter cell

Question 36

Tissue culture experiments with PDGF demonstrate that without this substance ( ).

Answer 36

Fibroblasts fail to divide

Question 37

Observations of cancer cells in culture support the hypothesis that cancer cells ( ).

Answer 37

Do not exhibit density-dependent inhibition

Question 38

Explain how cell division functions in reproduction, growth, and repair.

Answer 38

Cell division allows for 2 daughter cells to be formed, essentially making a copy of itself, which allows for different bodily processes to occur.

Question 39

Describe the structural organization of the genome.

Answer 39

"Genome" is the cell's DNA which is packaged into structures called chromosomes. In eukaryotic chromosomes, there is 1 long, linear DNA molecule with many proteins and has building materials of chromosomes (which are chromatin), then, 2 sister chromatids are made, and there is a centromere within the sister chromatids (where they are attached most closely)

Question 40

Describe the major events of cell division that enable the genome of one cell to be passed on to 2 daughter cells.

Answer 40

1. replicate DNA 2. long, thin chromatin fiber becomes condensed (coiled and folded). 3. creates 2 sister chromatids 4. sister chromatids separate and move into 2 new nuclei (one forming at each end of the cell). 5. mitosis (division of genetic material) 6. cytokinesis (division of cytoplasm)

Question 41

Describe how the chromosome number changes throughout the human life cycle

Answer 41

You inherit 46 chromosomes, then you have 23 chromosomes, and when fertilized, someone has 46 chromosomes again

Question 42

Somatic cells

Answer 42

All body cells except reproductive cells

Question 43

Gametes

Answer 43

Reproductive cells

Question 44

List the phases of the cell cycle and describe the sequence of events that occur during each phase

Answer 44

1. mitotic phase (mitosis and cytokinesis) ; shortest 2. interphase ; grows + copies chromosomes ; 90% a) G1 phase ("first gap"): cell grows b) S phase ("synthesis"): cell continues to grow + duplicate chromosomes c) G2 phase ("second gap"): cell grows more + completes preparation for cell division d) M phase: divides

Question 45

List the phases of mitosis

Answer 45

G2 of interphase, prophase, premetaphase, metaphase, anaphase, telophase and cytokinesis

Question 46

G2 of interphase

Answer 46

nuclear envelope encloses nucleus, then nucleus contains 1 or more nucleoli (nucleolus), 2 centrosomes made through duplication (centrosomes are organized microtubules of spindle; containing 2 centrioles)

Question 47

Prophase

Answer 47

chromatin fibers become more tightly coiled, condensing into discrete chromosomes, then nucleoli disappear and each duplicated chromosome appears joined at centromeres, and in some species, joined at arms by cohesion (sister chromatid cohesion), mitotic spindle begins to form centrosomes + microtubules that extend from them = asters ("stars"), centrosomes move away from each other because of the microtubules between them

Question 48

Premetaphase

Answer 48

the nuclear envelope fragments, microtubules extending from each centrosome can now invade nuclear area, chromosomes = more condensed, each chromatid has kinetochore (specialized protein structure at centromere, some microtubules attach to kinetochore ("kinetochore microtubules"); jerk chromosomes back and forth

Question 49

metaphase

Answer 49

centrosomes at opposite poles of the cell, chromosomes meet at metaphase plate (equidistant between 2 poles0, centromeres are there, each chromosome's kinetochores are attached to kinetochore microtubules

Question 50

anaphase

Answer 50

shortest stage of mitosis ( a few minutes); cohesion proteins are cleaved, so 2 sister chromatids of each pair suddenly part, each chromatid becomes an individual chromosome, the 2 chromosomes move to opposite ends, then the cell elongates as nonkinetochore microtubules lengthen, then the two ends of the cell have equivalent and complete collections of chromosomes.

Question 51

telephase and cytokinesis

Answer 51

the two sister chromatids split apart with cleavage furrow and nuclear envelope begins forming along with the two nucleolus'

Question 52

Process of binary fission in bacteria and how this process may have evolved in eukaryotic mitosis. Regulation of the cell cycle.

Answer 52

binary fission in bacteria: 1) "division in half" : eukaryotes involve mitosis, prokaryotes do not 2) in bacteria, most genes on a single bacterial chromosome (circular DNA molecules + associated proteins) (a) DNA of bacterial chromosome begins to replicate at a specific place on chromosome (origin of replication), produce 2 origins (b) as chromosomes continue to replicate, one origin moves rapidly toward each end of the cell (c) while chromosomes replicate, the cell elongates (d) replication completes: the bacterium = 2x the original size, then the plasma membrane pinches inward and 2 daughter cells are formed

Question 53

Describe the roles of checkpoints, cyclin, cdk, and MPF in the cell cycle control system

Answer 53

cell cycle control system: a cyclically operating set of molecules that triggers and coordinates key events checkpoint: stop/go-ahead signals regulate cell cycle cyclin: allows a kinase to be active; these kinases are called "cyclin-dependent kinases" (cdk) MPF: (maturation-promoting factor); but think of it as "M phase promoting factor"

Question 54

Internal/external factors that influence cell cycle control system

Answer 54

Density-dependent inhibition (crowded cells stop dividing), causing cancer