Everything

Question 2

Question: What four events characterize cell division in both prokaryotes and eukaryotes? Answer: The four events that characterize cell division are: cell division signals

Answer 2

DNA replication

Question 3

Question: What is required to initiate cell division? Answer: One or more signals are required to initiate cell division

Answer 3

which may originate from either inside or outside the cell.

Question 4

Question: Why must a dividing cell replicate its DNA? Answer: The dividing cell’s genetic material (DNA) must be duplicated so that each of the two new cells will have a full complement of genetic information.

Question 5

Question: What must happen to the replicated DNA during cell division? Answer: The replicated DNA must be distributed appropriately (segregated) to the two daughter cells

Answer 5

so that each receives a copy of every chromosome.

Question 6

Question: What is cytokinesis? Answer: Cytokinesis is the division of the cytoplasm to form the two new cells

Answer 6

each surrounded by a cell membrane

Question 7

Question: How does cell division result in reproduction in prokaryotes? Answer: In prokaryotes

Answer 7

cell division by binary fission results in the reproduction of the entire single-celled organism.

Question 8

Question: What are common signals for the initiation of cell division in prokaryotes? Answer: External factors such as environmental conditions and nutrient concentrations are common signals for the initiation of cell division in prokaryotes.

Question 9

Question: What conditions allow Bacillus subtilis to divide rapidly? Answer: Bacillus subtilis can divide in under an hour if abundant sources of carbohydrate and mineral nutrients are available and if the pH and temperature are optimal.

Question 10

Question: How quickly can Escherichia coli divide under optimal conditions? Answer: Escherichia coli can divide every 20 minutes under optimal conditions.

Question 11

Question: What is a chromosome in prokaryotes? Answer: A chromosome in prokaryotes consists of a long

Answer 11

thin DNA molecule that contains the genetic information for the organism

Question 12

Question: How many main chromosomes do most prokaryotes have? Answer: Most prokaryotes have just one main chromosome.

Question 13

Question: What must happen to the prokaryotic chromosome before cell division? Answer: When a prokaryotic cell divides

Answer 13

its chromosome must be replicated

Question 14

Question: How is bacterial DNA compacted to fit inside the cell? Answer: Bacterial DNA folds in on itself

Answer 14

and positively charged (basic) proteins bound to the negatively charged (acidic) DNA contribute to this folding.

Question 15

Question: What are the two regions of the prokaryotic chromosome that play functional roles in cell reproduction? Answer: The two regions are: ori (the site where replication starts) and ter (the site where replication ends).

Question 16

Question: Where does chromosome replication take place in prokaryotes? Answer: Chromosome replication takes place as the DNA is threaded through a replication complex of proteins near the center of the cell.

Question 17

Question: In which direction does replication proceed from the ori site in prokaryotes? Answer: Replication begins at the ori site and moves bidirectionally toward the ter site.

Question 18

Question: What happens to the two daughter DNA molecules after replication in prokaryotes? Answer: When replication is complete

Answer 18

the two daughter DNA molecules separate and segregate from one another at opposite ends of the cell.

Question 19

Question: What happens to the ori regions once DNA replication begins in prokaryotes? Answer: Once replicated

Answer 19

the ori regions move toward opposite ends of the cell as replication of the rest of the parent molecule proceeds.

Question 20

Question: What is essential for the segregation of DNA in prokaryotes

Answer 20

and what powers this process? Answer: DNA sequences adjacent to each of the ori regions bind proteins that are essential for segregation. This is an energy-requiring process

Question 21

Question: When does cytokinesis begin in prokaryotes relative to chromosome replication? Answer: Cytokinesis begins immediately after chromosome replication is finished.

Question 22

Question: How does the cell membrane pinch in during prokaryotic cytokinesis? Answer: The cell membrane pinches in to form a ring of fibers

Answer 22

termed the Z ring

Question 23

Question: What is the major component of the Z ring in prokaryotes? Answer: The major component of the Z ring is a protein called FtsZ that is related to eukaryotic tubulin.

Question 24

Question: What happens after the cell membrane pinches in during prokaryotic cytokinesis? Answer: As the membrane pinches in

Answer 24

new cell wall materials are deposited

Question 25

Question: What are the four events of cell reproduction in eukaryotes? Answer: The four events are: cell division signals

Answer 25

DNA replication

Question 26

Question: How do cell division signals differ between single-celled and multicellular eukaryotes? Answer: Single-celled eukaryotes often undergo cell division when environmental conditions are appropriate. In multicellular eukaryotes

Answer 26

while internal conditions may be suitable

Question 27

Question: How does the amount of DNA and the number of chromosomes differ between prokaryotes and eukaryotes? Answer: Eukaryotes have more DNA than prokaryotes

Answer 27

and it is contained in more than one chromosome (e.g.

Question 28

Question: What are the two major differences in DNA replication between eukaryotes and prokaryotes? Answer: First

Answer 28

eukaryotic DNA replication starts at numerous origins of replication

Question 29

Question: How is DNA segregation accomplished in eukaryotes? Answer: Because eukaryotes have multiple chromosomes

Answer 29

a mechanism called mitosis segregates the two sets of DNA molecules produced by replication into two new nuclei.

Question 30

Question: What happens to chromosomes before segregation in eukaryotes? Answer: Chromosomes become highly condensed before they segregate

Answer 30

which makes them easier to move into the two new nuclei.

Question 31

Question: What cytoskeletal structure is involved in moving chromosomes during eukaryotic segregation? Answer: The spindle

Answer 31

a special cytoskeletal structure composed of microtubules

Question 32

Question: How does cytokinesis differ between plant and animal cells? Answer: Cytokinesis proceeds differently in plant cells (which have a cell wall) than in animal cells (which do not).

Question 33

Question: What is the outcome in terms of DNA content of the cells resulting from mitosis? Answer: The cells resulting from mitosis are identical to the parent cell in the amount and kind of DNA they contain.

Question 34

Question: What is another mechanism for nuclear division in eukaryotes

Answer 34

and what is its role? Answer: Another mechanism is meiosis

Question 35

Question: What are the four events required for cell division? Answer: Cell division signals

Answer 35

replication of DNA

Question 36

Question: What commonly controls whether a prokaryotic cell will begin binary fission? Answer: Environmental conditions and nutrient availability commonly control whether a prokaryotic cell will begin binary fission.

Question 37

Question: Why must DNA be replicated and segregated before a cell can divide? Answer: DNA must be replicated so that each daughter cell receives a full complement of genetic information. It must be segregated to ensure that each daughter cell receives a copy of every chromosome.

Question 38

Question: Why are DNA replication and cell division more complex in eukaryotes than in prokaryotes? Answer: Eukaryotes have more DNA contained in multiple linear chromosomes

Answer 38

requiring more intricate mechanisms for replication initiation and chromosome segregation (mitosis).

Question 39

Question: What determines whether a eukaryotic cell will divide? Answer: In multicellular eukaryotes

Answer 39

cell division signals are related to the function of the entire organism

Question 40

Question: What is the eukaryotic cell cycle? Answer: The eukaryotic cell cycle is the series of phases through which a single cell passes to produce daughter cells by cell division.

Question 41

Question: What are the four phases of the eukaryotic cell cycle? Answer: The four phases are G1

Answer 41

S

Question 42

Question: What does the M phase of the cell cycle include? Answer: The M phase includes mitosis and cytokinesis.

Question 43

Question: What three phases make up interphase? Answer: The three phases that make up interphase are G1

Answer 43

S

Question 44

Question: What occurs during interphase? Answer: During interphase

Answer 44

the cell nucleus is visible and typical cell functions occur

Question 45

Question: How does the duration of the cell cycle vary in different cell types? Answer: The duration of the cell cycle varies considerably; for example

Answer 45

it may be as short as 30 minutes in an early embryo or about 24 hours in rapidly dividing adult human cells.

Question 46

Question: Which phase of the cell cycle do cells typically spend most of their time in? Answer: In general

Answer 46

cells spend most of their time in interphase.

Question 47

Question: What happens during the G1 phase of the cell cycle? Answer: During G1 phase

Answer 47

each chromosome is a single

Question 48

Question: What accounts for most of the variability in the length of the cell cycle in different cell types? Answer: Variations in the duration of the G1 phase account for most of the variability.

Question 49

Question: What happens at the G1-to-S transition? Answer: At the G1-to-S transition

Answer 49

the commitment is made to DNA replication and subsequent cell division.

Question 50

Question: What occurs during the S phase of the cell cycle? Answer: DNA replication occurs during S phase

Answer 50

and each chromosome is duplicated

Question 51

Question: What are sister chromatids

Answer 51

and when do they segregate? Answer: Sister chromatids are the products of DNA replication and remain joined together until mitosis

Question 52

Question: What happens during the G2 phase of the cell cycle? Answer: During G2 phase

Answer 52

the cell makes preparations for mitosis

Question 53

Question: What happens to cells that do not divide? Answer: Cells that do not divide usually arrest during G1 and enter G0

Answer 53

an inactive resting phase.

Question 54

Question: Can cells in G0 re-enter the cell cycle? Answer: Yes

Answer 54

cells in G0 can sometimes return to G1 and the rest of the cell cycle under certain environmental conditions

Question 55

Question: Give examples of human cells that typically stay in G0. Answer: Examples include cells of the heart (cardiac muscle) and brain (neurons).

Question 56

Question: What did cell fusion experiments with HeLa cells reveal about the cell cycle? Answer: Cell fusion experiments revealed the existence of internal signals that control the transitions between stages of the cell cycle

Answer 56

such as a substance in S phase that activates DNA replication.

Question 57

Question: What are cyclin-dependent kinases (CDKs)? Answer: Cyclin-dependent kinases (CDKs) are protein kinases that control the progress through the cell cycle.

Question 58

Question: How is a CDK activated? Answer: A CDK is not enzymatically active unless it is bound to another class of protein

Answer 58

the activators called cyclins.

Question 59

Question: What is the role of phosphorylation in cell cycle regulation by CDKs? Answer: Cyclin–CDK complexes catalyze the phosphorylation of target proteins

Answer 59

and this phosphorylation regulates their activity and thus the progression through different stages of the cell cycle.

Question 60

Question: What is the restriction point (R) in the cell cycle? Answer: The restriction point (R) is a control point in the cell cycle that occurs at the G1-to-S transition

Answer 60

controlled by a particular CDK.

Question 61

Question: What is the role of the retinoblastoma protein (RB) at the restriction point? Answer: In many cells

Answer 61

RB acts as an inhibitor of the cell cycle at the restriction point (R).

Question 62

Question: How is the RB protein inactivated to allow the cell cycle to proceed to S phase? Answer: The G1/S cyclin–CDK catalyzes the phosphorylation of RB

Answer 62

causing a change in its structure and inactivating it

Question 63

Question: How are CDKs regulated? Answer: An effective way to regulate CDKs is to regulate the presence or absence of cyclins

Answer 63

which are present cyclically.

Question 64

Question: What are cell cycle checkpoints? Answer: Cell cycle checkpoints are signaling pathways that regulate the cell cycle’s progress

Answer 64

ensuring that critical events like DNA replication and chromosome segregation are completed correctly before the cycle advances.

Question 65

Question: What might cause a cell cycle to pause at a checkpoint during interphase? Answer: Substantial DNA damage caused by radiation or toxic chemicals might cause the cell cycle to pause. Incomplete replication or DNA damage can also trigger a checkpoint in the S phase.

Question 66

Question: Describe the role of the p21 protein in the G1-to-S checkpoint. Answer: If DNA is damaged during G1

Answer 66

a signaling pathway results in the production of p21 protein. P21 binds to the G1/S CDK

Question 67

Question: What happens if DNA damage is severe and cannot be repaired? Answer: If DNA damage is severe and cannot be repaired

Answer 67

the cell will undergo programmed cell death (apoptosis).

Question 68

Question: What are growth factors? Answer: Growth factors are external chemical signals that can stimulate cells that are in G0 or dividing infrequently to go through the cell cycle.

Question 69

Question: Provide examples of how growth factors stimulate cell division. Answer:

Question 70

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Question 71

Platelet-derived growth factor released by platelets at a wound stimulates adjacent skin cells to divide and heal the wound.

Question 72

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Question 73

Interleukins stimulate the division of precursor cells of white blood cells in bone marrow.

Question 74

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Question 75

Erythropoietin stimulates the division and specialization of precursor cells of red blood cells in bone marrow.

Question 76

Question: How do growth factors activate the cell cycle? Answer: Growth factors bind to specific receptors on target cells and activate signal transduction pathways that end with cyclin synthesis

Answer 76

thereby activating CDKs and the cell cycle.

Question 77

Question: What is chromatin? Answer: Chromatin is the complex of DNA and proteins (especially histones) that make up a eukaryotic chromosome.

Question 78

Question: How does DNA packaging vary during the cell cycle? Answer: During interphase

Answer 78

chromatin is less compact

Question 79

Question: What are sister chromatids

Answer 79

and when are they present in the cell cycle? Answer: Sister chromatids are two identical double-stranded DNA molecules that are the products of DNA replication during S phase. They are present from the end of S phase through G2 and until they separate during anaphase of mitosis.

Question 80

Question: What holds sister chromatids together along most of their length? Answer: Sister chromatids are held together along most of their length by a protein complex called cohesin.

Question 81

Question: Where do sister chromatids remain held together at mitosis? Answer: Sister chromatids remain held together at the centromere during mitosis.

Question 82

Question: What are condensins? Answer: Condensins are a group of proteins that coat DNA molecules at the end of G2 and the beginning of mitosis

Answer 82

making them more compact.

Question 83

Question: What are histones? Answer: Histones are positively charged proteins that bind to negatively charged DNA and help in DNA packaging by forming nucleosomes.

Question 84

Question: What are nucleosomes? Answer: Nucleosomes are beadlike units formed by DNA wrapped around a core of eight histone molecules.

Question 85

Question: Why is DNA less accessible during mitosis compared to interphase? Answer: The compact nature of mitotic chromosomes makes DNA inaccessible to replication and transcription factors.

Question 86

Question: What is the purpose of mitosis? Answer: Mitosis ensures the accurate segregation of each copy of a eukaryotic cell’s multiple chromosomes into two daughter nuclei that are genetically identical to each other and to the parent cell.

Question 87

Question: What are the five stages of mitosis? Answer: The five stages of mitosis are prophase

Answer 87

prometaphase

Question 88

Question: What are centrosomes? Answer: Centrosomes are organelles in the cytoplasm near the nucleus that organize the spindle and determine the plane of cell division in animal cells.

Question 89

Question: What do centrosomes consist of in many organisms? Answer: In many organisms

Answer 89

the centrosome consists of a pair of centrioles

Question 90

Question: What happens to centrosomes during S phase and prophase? Answer: During S phase

Answer 90

the centrosome duplicates

Question 91

Question: What are spindle fibers (mitotic spindle)? Answer: The spindle is a dynamic microtubule structure that moves sister chromatids apart during mitosis.

Question 92

Question: What role do microtubule organizing centers play in plant and fungi cells during mitosis? Answer: Plant and fungi cells lack centrosomes

Answer 92

but distinct microtubule organizing centers at each end of the cell play the same role in spindle formation.

Question 93

Question: How do the positions of centrosomes relate to cell division in animal cells? Answer: The positions of the centrosomes determine the plane where the animal cell will divide.

Question 94

Question: What happens to the nucleus during prophase? Answer: During prophase

Answer 94

chromatin condenses into visible chromosomes

Question 95

Question: What specialized structures develop in the centromere region during late prophase? Answer: Kinetochores develop in the centromere region

Answer 95

one on each chromatid.

Question 96

Question: What are kinetochores important for? Answer: Kinetochores are important for chromosome movement during mitosis.

Question 97

Question: What happens to microtubules during prophase and prometaphase? Answer: During prophase and prometaphase

Answer 97

microtubules form between the poles and the chromosomes to make up the spindle.

Question 98

Question: What are the two groups of microtubules in the spindle? Answer: The two groups are polar microtubules and kinetochore microtubules.

Question 99

Question: What is the function of polar microtubules? Answer: Polar microtubules form the framework of the spindle and run from one pole to the other.

Question 100

Question: What is the function of kinetochore microtubules? Answer: Kinetochore microtubules attach to the kinetochores on the chromosomes.

Question 101

Question: How do sister chromatids become attached to the spindle? Answer: The two sister chromatids in each replicated chromosome become attached to kinetochore microtubules from opposite poles.

Question 102

Question: What happens during prometaphase? Answer: During prometaphase

Answer 102

the nuclear envelope breaks down

Question 103

Question: What happens during metaphase? Answer: During metaphase

Answer 103

the chromosomes line up at the equatorial position (metaphase plate) of the cell.

Question 104

Question: What controls the separation of chromatids at the beginning of anaphase? Answer: The separation of chromatids is controlled by an M phase cyclin–CDK

Answer 104

which activates another protein complex called the anaphase-promoting complex (APC).

Question 105

Question: What is separase? Answer: Separase is a specific protease that hydrolyzes one subunit of the cohesin protein holding sister chromatids together

Answer 105

allowing them to separate.

Question 106

Question: What is the spindle assembly checkpoint? Answer: The spindle assembly checkpoint occurs at the end of metaphase to inhibit the APC if one of the chromosomes is not attached properly to the spindle.

Question 107

Question: What are sister chromatids called after they separate? Answer: After separation

Answer 107

sister chromatids are called daughter chromosomes.

Question 108

Question: What is the difference between sister chromatids and daughter chromosomes? Answer: Sister chromatids share a centromere

Answer 108

while daughter chromosomes have their own centromere.

Question 109

Question: Describe the three mechanisms that operate to move daughter chromosomes to the poles during anaphase. Answer:

Question 110

•

Question 111

Kinetochores contain molecular motor proteins (kinesins and dynein) that move chromosomes along microtubules.

Question 112

•

Question 113

Kinetochore microtubules shorten

Answer 113

drawing the chromosomes toward the poles.

Question 114

•

Question 115

Centrosomes move apart

Answer 115

aiding in separation.

Question 116

Question: What happens during telophase? Answer: During telophase

Answer 116

the spindle disappears

Question 117

Question: How does cytokinesis occur in animal cells? Answer: Cytokinesis in animal cells begins with a furrowing of the cell membrane caused by a contractile ring composed of actin and myosin microfilaments that pinches the cell in two.

Question 118

Question: How does cytokinesis occur in plant cells? Answer: In plant cells

Answer 118

vesicles derived from the Golgi apparatus fuse to form a cell plate midway between the two daughter nuclei. The cell plate grows outward and develops into a new cell wall

Question 119

Question: What happens to organelles during cytokinesis? Answer: Organelles such as ribosomes

Answer 119

mitochondria

Question 120

Question: What is asexual reproduction based on? Answer: Asexual reproduction is based on the mitotic division of the nucleus.

Question 121

Question: What are clones in the context of asexual reproduction? Answer: Clones are new organisms that are genetically identical to the parent produced by asexual reproduction.

Question 122

Question: Give an example of an organism that reproduces asexually. Answer: Examples include yeast (single-celled) and aspen trees (multicellular).

Question 123

Question: What is sexual reproduction? Answer: The sexual life cycle involves meiosis and fertilization.

Question 124

Question: What are haploid and diploid cells? Answer: Haploid (n) cells have one set of chromosomes

Answer 124

while diploid (2n) cells have two sets of chromosomes (homologous pairs).

Question 125

Question: What are gametes? Answer: Gametes are haploid reproductive cells (e.g.

Answer 125

sperm and eggs) formed by meiosis.

Question 126

Question: What is fertilization? Answer: Fertilization is the fusion of two haploid gametes to form a diploid zygote.

Question 127

Question: What is meiosis? Answer: Meiosis is a type of cell division that reduces the chromosome number from diploid to haploid

Answer 127

producing four genetically distinct daughter cells (gametes in animals).

Question 128

Question: How does the amount of DNA in daughter cells produced by meiosis compare to the parent cell? Answer: Meiosis produces four daughter cells

Answer 128

each carrying half the amount of DNA as the original G1 parent cell.

Question 129

Question: What happens to homologous chromosomes during meiosis I? Answer: During meiosis I

Answer 129

homologous chromosomes pair during synapsis and separate

Question 130

Question: How does meiosis II compare to mitosis? Answer: Meiosis II is similar to mitosis in that sister chromatids separate

Answer 130

resulting in four haploid cells. However

Question 131

Question: What is nondisjunction? Answer: Nondisjunction is the failure of chromosomes to separate properly during mitosis or meiosis.

Question 132

Question: What can be the result of nondisjunction? Answer: Nondisjunction can result in aneuploidy (an abnormal number of chromosomes in a cell) or polyploidy (if all chromosomes are involved

Answer 132

resulting in more than two sets of chromosomes).

Question 133

Question: What is polyploidy

Answer 133

and how might it arise? Answer: Polyploidy is a condition in which a cell or organism has more than two complete sets of chromosomes. It can arise from nondisjunction of all chromosomes during mitosis in a diploid zygote

Question 134

Question: What are some examples of polyploid crop plants? Answer: Examples include wheat

Answer 134

cotton

Question 135

Question: What are the two ways a cell may die? Answer: A cell may die by necrosis or by genetically programmed apoptosis.

Question 136

Question: What is necrosis? Answer: Necrosis occurs when cells and tissues are damaged by mechanical means

Answer 136

toxins

Question 137

Question: What is apoptosis? Answer: Apoptosis

Answer 137

or programmed cell death

Question 138

Question: Give examples of when apoptosis is necessary in animals. Answer: Apoptosis is necessary for:

Question 139

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Question 140

Removing cells that are no longer needed by the organism

Answer 140

such as connective tissue between fingers in a fetus.

Question 141

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Question 142

Removing cells that may have accumulated genetic damage and could lead to cancer

Answer 142

such as epithelial cells.

Question 143

Question: What are the events of apoptosis in animal cells? Answer: The events include: the cell detaching from neighbors

Answer 143

chromatin digestion into fragments of about 180 base pairs

Question 144

Question: How does apoptosis differ in plant cells compared to animal cells? Answer: Plant cells do not form blebs due to their rigid cell walls. Instead

Answer 144

they digest their own cell contents in the vacuole and then release the digested components into the vascular system

Question 145

Question: What types of signals can lead to apoptosis? Answer: Signals can be external (e.g.

Answer 145

hormones

Question 146

Question: What is a common target of apoptotic pathways within the cell? Answer: Some apoptotic pathways target the mitochondria

Answer 146

for example

Question 147

Question: What are caspases? Answer: Caspases are an important class of enzymes (proteases) that are activated during apoptosis and hydrolyze target molecules in a cascade of events

Answer 147

leading to cell death.

Question 148

Question: How do cancer cells differ from normal cells? Answer: Cancer cells differ in two main ways: they lose control over cell growth and they can migrate to other locations in the body (metastasis).

Question 149

Question: What are tumors? Answer: Tumors are large masses of cells formed by the uncontrolled division of cancer cells.

Question 150

Question: What is the difference between benign and malignant tumors? Answer: Benign tumors grow slowly

Answer 150

resemble the tissue they came from

Question 151

Question: What is metastasis? Answer: Metastasis is the spreading of cancer cells to other parts of the body through the bloodstream or lymphatic ducts

Answer 151

where they form new tumors.

Question 152

Question: What are positive and negative regulators of the cell cycle? Answer: Positive regulators (like growth factors) stimulate the cell cycle

Answer 152

acting like "gas pedals." Negative regulators (like retinoblastoma protein RB) inhibit the cell cycle

Question 153

Question: What are oncogenes? Answer: Oncogenes are mutated forms of normal positive regulators (proto-oncogenes) that are overly active or present in excess in cancer cells

Answer 153

stimulating increased cell division.

Question 154

Question: Give an example of an oncogene protein in breast cancer. Answer: An example is the HER2 growth factor receptor

Answer 154

which is overproduced in about 25% of breast cancers

Question 155

Question: What are tumor suppressor genes? Answer: Tumor suppressor genes encode negative regulators of the cell cycle. In cancer cells

Answer 155

these genes are often inactive or mutated

Question 156

Question: Give examples of tumor suppressor proteins and how they are inactivated in cancer. Answer:

Question 157

•

Question 158

Retinoblastoma protein (RB) normally inhibits the cell cycle at the restriction point. In some cancer cells

Answer 158

RB is inactive

Question 159

•

Question 160

p53 is a transcription factor involved in cell cycle checkpoints and apoptosis. Mutations in the p53 gene are found in more than 50% of human tumors.

Question 161

Question: What is the relationship between cell division rate and apoptosis rate in normal nongrowing tissues? Answer: In normal nongrowing tissues

Answer 161

the rate of cell division equals the rate of apoptosis

Question 162

Question: How do cancer cells' regulation of cell division and apoptosis differ from normal cells? Answer: Cancer cells have a defective regulation of the cell cycle

Answer 162

leading to increased rates of cell division. They can also lose the ability to respond to positive regulators of apoptosis

Question 163

Question: How do most cancer treatments work? Answer: Most cancer treatments generally target the cell cycle to decrease the rate of cell division and/or increase the rate of apoptosis in cancer cells.

Question 164

Question: Give examples of cancer drugs that target the cell cycle and their mechanisms. Answer:

Question 165

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Question 166

5-fluorouracil blocks the synthesis of thymine

Answer 166

inhibiting DNA replication.

Question 167

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Question 168

Paclitaxel prevents the functioning of microtubules in the mitotic spindle.

Question 169

Question: How does radiation treatment work to combat cancer? Answer: Radiation treatment uses high-energy radiation to cause extensive DNA damage in tumor cells

Answer 169

overwhelming the DNA repair checkpoints and leading to apoptosis.

Question 170

Question: What is a major problem with cancer treatments like chemotherapy and radiation? Answer: These treatments can affect normal dividing cells as well as tumor cells

Answer 170

leading to toxic side effects in tissues like the intestine

Question 171

Question: What is trastuzumab

Answer 171

and how does it target cancer cells? Answer: Trastuzumab is a cancer drug that specifically targets the HER2 growth factor receptor

Question 172

Question: How do cells in benign tumors differ from those in malignant tumors? Answer: Cells in benign tumors resemble normal tissue

Answer 172

grow slowly

Question 173

Question: Why might combining multiple drugs that target different stages of the cell cycle be a better cancer treatment approach? Answer: Targeting several stages of the cell cycle can increase the effectiveness of treatment by disrupting multiple processes necessary for cancer cell proliferation and survival

Answer 173

making it harder for cancer cells to develop resistance.

Question 174

Question: According to the "Investigating Life" section

Answer 174

what factors contribute to the extraordinary growth rate of HeLa cells? Answer: HeLa cells' rapid growth is attributed to a genetic imbalance favoring cell reproduction over cell death

Question 175

Question: Why are HeLa cells considered "just cell division machines" despite originating from a malignant tumor? Answer: The source suggests they might be missing something that tumor cells have for forming a tumor in a living organism in their current state

Answer 175

perhaps the ability to invade tissues or establish a blood supply in a new location.

Question 176

Question: What is a promising future direction in cancer treatment beyond targeting the cell cycle? Answer: Developing targeted drugs that specifically stimulate apoptosis only in tumor cells could be an effective treatment strategy with potentially fewer side effects than drugs that generally affect all dividing cells