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Biology 1A03 > Theme 4: DNA Replication and Mitosis - Module 1: The Cell Cycle > Flashcards

Theme 4: DNA Replication and Mitosis - Module 1: The Cell Cycle Flashcards

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1
Q

the ability of a pre-existing cell to give rise to another cell is due to what?

A

regulated process of cel division

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2
Q

for prokaryotes, what is cell division also considered?

A

reproduction

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3
Q

why is prokaryotic cell division also considered reproduction?

A

because cell division gives rise to a new organism (made up of one cell)

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4
Q

what are founding prokaryotic cells with regards to reproduction?

A

all essential elements necessary to reproduce

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5
Q

what are prokaryotic cells capable of?

A

making exact copies of their genomes and then segregating one copy of each genome to each two daughter cells

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6
Q

what does the process of cell division in prokaryotes require?

A

identical genetic material distributed amongst the daughter cells

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7
Q

what is the process of cell division in prokaryotes a form of?

A

asexual reproduction

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8
Q

what is the asexual reproduction of prokaryotes referred to as?

A

binary fission

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9
Q

when is the process of cell division in prokaryotes initiated?

A

when the DNA of the bacterial chromosome is attached by proteins to the inside of the plasma membrane

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10
Q

where does DNA replication begin?

A

along an origin of replication region of the bacterial chromosome

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11
Q

what occurs as the chromosome continue to replicate?

A

cell begins to elongate and newly synthesized DNA is also anchored to the plasma membrane

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12
Q

how long does the cell continue to elongate for?

A

until the two DNA attachment sites are at opposite ends of the elongated cell

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13
Q

when DNA replication is complete and the bacterium is around double its size what does the bacterial cell begin to do?

A

bacterial cell begins to constrict along the midpoint of the cell

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14
Q

what is the constriction of the cell accompanied by?

A

the synthesis of new cell membrane and wall - leads to complete division of the two identical daughter cells

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15
Q

what does the regulated process in eukaryotes refereed to as ?

A

mitosis

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16
Q

what does division in eukaryotic cells allow for?

A

unicellular fertilized egg to develop into a complex multicellular organism

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17
Q

what do early embryos contain?

A

stem cells

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18
Q

what are stem cells?

A

unspecialized cells that can both reproduce indefinitely and under appropriate conditions

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19
Q

what are stem cells able to do?

A

able to differentiate into specialized cells of one of one or more types

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20
Q

what can cell division lead to after an organism is fully grown?

A

lead to continual renewal and repair of cells that make up various tissues

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21
Q

are there adult stem cells?

A

yes

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22
Q

what are adult stem cells not able to do?

A

not able to give rise to all cell types in the organism

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23
Q

what are adult stem cells able to do?

A

replace non-responding specialized cells

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24
Q

explain the property of the adult skeletal muscle

A

stable tissue with little cell turnover

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25
Q

what happens when muscle cells undergo injury

A

quiescent (non-dividing) satellite stem cells that are present in the basement membrane of the muscle tissue are able to become activated and begin diving again to enable muscle regeneration

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26
Q

what does the activation of the satellite cells lead to?

A

proliferation, differentiation, and fusion of muscle precursor cells

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27
Q

what are the muscle precursor cells called

A

myoblasts

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28
Q

what to the my blasts eventually become committed to forming?

A

the mature muscle cells that make up the muscle fibers (myofibers)

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29
Q

what happens when the myofibers are formed?

A

no longer able to divide

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30
Q

what is one of the main distinctions between prokaryotic and eukaryotic cell division?

A
  • eukaryotic DNA is larger
  • organized into linear chromosomes
  • highly condensed into the nucleus of the cell
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31
Q

what does the process of cell division in eukaryotes require? why?

A
  • more regulated control

- larger cell cycle

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32
Q

how many distinct stages does the eukaryotic cell cycle consist of?

A

two

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33
Q

what is one of the stages?

A

interphase

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34
Q

what does this stage consist of?

A
  • S phase
  • 2 gap growth phases G1 and G2
  • M phase
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35
Q

what occurs in the S phase?

A

DNA synthesis

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36
Q

what occurs in the M phase?

A

mitosis and cytokinesis

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37
Q

what must occur with each mitotic cell division?

A

the linear chromosome of eukaryotes must be replicated and then separated into daughter cells

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38
Q

what occurs in during the interphase stage?

A

cells prepare for cell division

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39
Q

how do cells prepare for cell division?

A
  • replication of DNA in nucleus

- overall increase in cell size

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40
Q

where does replication of DNA occur?

A

in the S (synthesis) phase

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41
Q

what do the G1 and G2 phases prepare the cell for?

A

DNA synthesis and mitosis

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42
Q

how long does it take for specific cells to pass through the cell cycle?

A

depends on the type of cells in question

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43
Q

do all cells participate in regular cell cycle that leads to regular divisions?

A

no

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44
Q

can cells pause in the cycle? if so, in what phase?

A

yes

G0 phase

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45
Q

what happens with cells in the G0 phase?

A

they pause somewhere between the M and S phase

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46
Q

how long is the pause?

A

wide range - can be short or long (days - years)

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47
Q

what are considered non-dividing cells?

A

cells that enter the G0 phase permanently

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48
Q

what type of cells enter a permanent G0 phase?

A
  • cells that make up the lenses of our eyes
  • nerve cells
  • mature muscle cells
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49
Q

can stem cells reproduce indefinitely?

A

yes

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50
Q

do stem cells have periods of quiescence and thus undergo no cell division?

A

yes

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51
Q

is it true that skeletal muscles have little to no cell division?

A

yes

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52
Q

what happens when an injury occurs?

A

the quiescent satellite stem cells are activated from the dormant G0 phase of the cell cycle and reenter the cell cycle

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53
Q

with the cells reentering the cell cycle what occurs as a result?

A

enables proliferation, differentiation and maturation of new muscle cell precursors that can fuse and repair the muscle tissue with new muscle fibres

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54
Q

what happens once the myofibers are formed?

A

they exit the cell cycle and enter the quiescent G0 phase

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55
Q

how many stages does mitosis consist of?

A

five

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56
Q

how can these stages characterized?

A

can be morphometrically characterized based on the distinctive changes that occur to the chromosomes that are involved in the cell division process

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57
Q

what did Walther Flemming discover?

A

distinct stages of mitosis could be staged based on chromosomal position and features

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58
Q

due to Flemmings work on salamander embryos, we know the five stages of mitosis, what are they?

A
  • prophase
  • prometaphase
  • metaphase
    anaphase
    telophase
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59
Q

what must occur before entering mitosis?

A

chromosomes of cells must be duplicated and condensed

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60
Q

why must the chromosomes of cells be duplicated and condensed before entering mitosis?

A

to allow for the daughter cells to acquire the same amount of genetic information as the parent cell in a relatively short period of time

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61
Q

what form is each chromosome in during most of interphase?

A

a long, thin chromatin fiber

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62
Q

what occurs prior to mitosis?

A

exact copies of every chromosome are created

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63
Q

what phase are the copies of the exact chromosome created in? through what process?

A
  • S phase

- process of DNA replication

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64
Q

where are DNA sequences replicated from?

A

end to end of the DNA molecule

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65
Q

what are the newly synthesized molecules associated with?

A

histones and other chromosomal proteins that allow for tight compaction

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66
Q

is the centromere fully replicated?

A

yes

67
Q

why do the paired centromeres appear fused together?

A

because they’re so highly compact

68
Q

when chromosomes are duplicated into two identical copies what are they referred to as?

A

sister chromatids

69
Q

what allows us to have 23 distinct chromosome pairs?

A

since we inherit a paternal and maternal chromosome

70
Q

how many homologous chromosomes do we have?

A

22 (one maternal and one paternal in origin)

71
Q

how many are sex chromosomes?

A

1

72
Q

what happens as a cell transitions from G2 to the M-phase?

A

duplicated chromosomes begin to condense and the individual chromosomes becomes visible even with a light microscope

73
Q

what is the first stage of mitosis?

A

prophase

74
Q

during prophase how will each chromosome appear?

A

as identical sister chromatids that are joined at their centromeres

75
Q

what are centromeres?

A

duplicated cellular microtubule organizing centres

76
Q

what do centromeres do in prophase?

A

radiate long microtubules forming a mitotic spindle

77
Q

where do centromeres become positioned?

A

at opposite poles of the cell

78
Q

what are the mitotic spindles crucial for?

A

separating the chromosomes into two daughter cells

79
Q

summarize prophase

A

chromosomes condensed - centrosomes radiate microtubules and migrate to opposite poles

80
Q

what follows prophase in mitosis?

A

prometaphase

81
Q

what is the defining feature of pro metaphase?

A

fragmentation of he nuclear envelope

82
Q

what are kinetochores?

A

specialized protein structures that associate with each one of the two sister chromatids on either side of the centromere

83
Q

what can occur because the nuclear envelope breaks down?

A

the microtubules that are extending from each centrosome as part of the mitotic spindle are able to attach to specialized region on the centromeres o the chromosome (referred to as kinetochores)

84
Q

is it true that some microtubules that radiate from the centrosome attach directly to the kinetochore regions?

A

yes

85
Q

what are the kinetochores essential for?

A

essential to help pull the chromosomes to the poles of the cell

86
Q

what are other microtubules that also radiate from the centrosome as part of the mitotic spindle?

A

polar microtubules

87
Q

what do polar microtubules do?

A

interact with each other and help push the poles of the cell away from each other

88
Q

summarize prometaphase?

A

microtubules of each mitotic spindle attach to chromosomes

- nuclear envelope starts to break down

89
Q

what is the third stage of mitosis?

A

metaphase

90
Q

what is metaphase marked by?

A

the alignment of chromosomes at the centre of the cell

91
Q

when the chromosomes are aligned at the centre of the cell what is this region identified as?

A

the metaphase plate

92
Q

what facilities the alignment at the metaphase plate?

A

the kinetochore microtubules of each chromosome are attached at the kinetochores of each sister chromatid

93
Q

what follows metaphase?

A

anaphase

94
Q

what happens to the kinetochore microtubules during anaphase?

A

begin to shorten

95
Q

what happens when the kinetochore microtubules begin to shorten?

A

the sister chromatids separate into individual chromosomes that are pulled towards the opposite spindle poles of the cell

96
Q

what do the polar microtubules do during anaphase?

A

they push against each other and help elongate the cell

97
Q

what is present at the end of anaphase?

A

the two ends of the cell will have equivalent and complete sets of chromosomes

98
Q

summarize anaphase

A

sister chromatids (which become individual chromosomes when the centromere splits) separate and travel to opposite poles

99
Q

what is the final stage of mitosis?

A

telophase

100
Q

what is telophase the stage of?

A

two new daughter nuclei form in the cell

101
Q

why does this occur?

A

because the nuclear envelope reforms around the chromosomes at the opposite poles of the dividing cell

102
Q

what happens to the chromosomes and spindle microtubules during telophase?

A
  • chromosomes begin to decondense

- spindle microtubules are depolymerized/broken down

103
Q

what marks the end of mitosis?

A

the division of one nucleus into two genetically identical nuclei

104
Q

what must follow the process of mitosis?

A

the division of the cell into two identical cells

105
Q

summarize telophase

A

nuclear envelope re-forms and chromosomes decondense

106
Q

what does the process of cytokinesis do?

A

division of cytoplasm and therefore the cell

107
Q

how does cytokinesis begin in animal cells?

A

with the formation of a contractile ring made up of motor proteins that contract bundles of actin fibers along the midline of the cell

108
Q

what does this lead to?

A

formation of a defined cleavage furrow

109
Q

what does a cleavage furrow do?

A

separates the cell into two distinct and seperate daughter cells

110
Q

are the stages of mitosis similar across all eukaryotic cell types?

A

yes

111
Q

where can differences in cytokinesis be observed?

A

depends on the dividing cell types

112
Q

is the process of cytokinesis distinct and different in plant and animal cells?

A

yes

113
Q

why is there a difference in cytogeneses between plant and animal cells?

A

plant cells have a cell wall

114
Q

what happens during cytokinesis of plant cells?

A

plant cells lay down a newly developed cell wall along a cell plate region in the middle of the diving cell

115
Q

when is cytogeneses complete in plant cells?

A

once the forming ell wall fuses with the original cell wall

116
Q

when is cell division important?

A

during developmental growth and with regards to maintenance and repair

117
Q

what did research in the 1970s begin to shed light on?

A

that there could be a mitosis promoting factor

118
Q

what would this mitosis promoting factor allow?

A

the transition from the G2 to M phase of the cell cycle

119
Q

what was studied in the 1980s?

A

protein level changes of dividing sea urchin embryos

120
Q

what did this research team do?

A
  • added radioactively labelled amino acids to the sea urchin eggs
  • research team was sure the radio labelled methionine would be incorporated into any newly synthesized proteins in the embryos
  • good way to measure protein changes in developing embryos
121
Q

when and how did the team observe changes?

A
  • took samples of rapidly dividing embryos every 10 minutes
  • visualized any changes in protein levels using gel electrophoresis (allows for distinct separation of different protein types)
122
Q

what did Hunt and his research team discover?

A

most protein bands on the gel became darker as cell division and embryonic development progressed

123
Q

what happened with one protein band?

A

oscillated in intensity

124
Q

what was found about the oscillating protein?

A

protein increased then decreased with each subsequent cell division

125
Q

what was this protein called?

A

cyclin (due to its cyclic nature)

126
Q

what did Hunt and researchers suspect this protein was involved in?

A

playing some sort of regulatory role on cell cycle progression

127
Q

what did follow up work by Hunt and his colleagues identify?

A

that the mitosis promoting factor consists of a cyclin protein and a cyclin-dependent kinase (CDK) protein - together they control progression of the cell cycle

128
Q

what is kinases?

A

enzymes that activate or inactive other proteins

129
Q

how do kinases activate or inactivate other proteins?

A

by phosphorylating key amino acids on the target proteins

130
Q

is it true that many kinases that regulate the cell cycle stay at a constant convention in the cell?

A

yes

131
Q

for much of the time are kinase active or inactive?

A

inactive

132
Q

how do kinase become active?

A

activated by binding to cyclin proteins

133
Q

how did kinase acquire the name cyclin-dependent kinases?

A

because the activity of the kinases is dependent on being bound to cyclins

134
Q

what can the cyclin-cyclin dependent kinase complex trigger? how is this done specifically?

A
  • the multitude of changes that occur during the various cell cycle events
  • by phosphorylation of target proteins that promote cell division
135
Q

what is the activity of the cyclin0dependent kinase?

A

it rises and falls with changes in the concentration of its activating cyclin protein

136
Q

is it true that there are many different types of cyclin-CDK complexes that are involved in the regulation of each stage of the cell cycle?

A

yes

137
Q

when is cyclin-CDK regulation important?

A

during three steps of the eukaryotic cell cycle

138
Q

what is the G1/S cyclin-CDK complex needed for?

A

the transition from the G1 to S phase and helps to prepare the cell for DNA replication (i.e. increasing the expression of histone proteins)

139
Q

what does the S-cyclin-CDK complex help with?

A

to initiate DNA synthesis

140
Q

what does the M cyclin-CDK complex initiate?

A

the process of mitosis

141
Q

what other key factors play an important role in the regulation of the cell cycle?

A

presence of multiple check points

142
Q

what do cell-cycle check points serve as?

A

form of cellular surveillance

143
Q

what are cell-cycle check points able to do?

A

block cyclin-CDK activity should something go wrong during the progression of the cell cycle

144
Q

what can cell-cycle check points do?

A

pause cell division

145
Q

how long can cell-cycle check points pause cell division?

A

until the preparation for the next stage of the cell cycle is complete

146
Q

what else can a cell-cycle check point serve as ?

A

opportunity for damage to be repaired

147
Q

what are the three major check point of the cell cycle?

A
  • DNA damage checkpoint at the end of G1 phase
  • DNA replication checkpoint at the end of the G2 phase
  • spindle assembly checkpoint before anaphase during mitosis
148
Q

due to cellular monitoring only what kind of DNA will be able to enter the S phase or replication due to the G1 checkpoint?

A

undamaged DNA

149
Q

due to G2 checkpoint when can a cell enter the mitosis phase?

A

only when all DNA is replicated

150
Q

due to the M phase checkpoint when will a cell complete mitosis?

A

if all chromosomes are attached to a microtubule from the mitotic spindle

151
Q

looking at an example of the DNA damage checkpoint, are the genes that normally inhibit cell cycle progression turned on or off?

A

off

152
Q

what is p53?

A

protein that can inhibit the cell cycle when turned on

153
Q

what happens when damage occurs to the structure of DNA (damage that includes double-stranded breaks in the phosphodiester backbone)

A

specific protein kinases are able to phosphorylate p53

154
Q

p53 protein is normally present in very high or very low levels in the nucleus? what is most of this protein doing?

A
  • very low levels

- most is being exported out of the nucleus degraded

155
Q

what happens during phosphorylation?

A

p53 is able to accumulate within the nucleus and acts as a transcription factor to turn on genes that will inhibit the cell cycle

156
Q

what does this lead to?

A

production of a CDK inhibitor protein

157
Q

what does the inhibitor protein do? what does this give the cell?

A
  • bind to and block the activity of the G1-S cyclin-CDK complex and thus stop/pause the cell cycle in the G1 phase
  • gives cell the opportunity to repair the damaged DNA
158
Q

spindle assembly example, as early as the pro metaphase stage of mitosis, regulatory proteins that are associated with the spindle assembly checkpoint are able to monitor what?

A

the degree to which the sister chromatids are attached to the microtubules of the mitotic spindle at their kinetochore regions

159
Q

what type of signal do unattached kinetochores create?

A

“wait” signal

160
Q

what does the “wait” signal lead to?

A

the recruitment of spindle-assembly check point proteins

161
Q

what are these proteins activated by?

A

lack of tension in the centromere area

162
Q

when is progression of metaphase and entry into anaphase allowed?

A

when each sister chromatid is attached to a kinetochore microtubule

163
Q

what happens when this occurs?

A

spindle checkpoint proteins are removed from the centromere region and separase, a specialized enzyme, is able to break sister chromatid attachments

Biology 1A03 (5 decks)

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