Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BMS 100 Physiology > Phys Concepts 1.17 > Flashcards

Phys Concepts 1.17 Flashcards

1
Q

What is the cell cycle?

A

The orderly sequence of events by which a cellduplicates its contents and divides in two

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

The cell cycle is driven by specific molecular signals present in the __

A

cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The cell cycle consists of 2 phases, what are they?

A
  • mitotic (M) phase (mitosis and cytokinesis)
  • interphase (cell growth and copying of chromosomes in preparation for cell division)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Interphase is about _% of the cell cycle

A

90

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Interphase can be divided in subphases, what are they?

A
  • G1 phase: first gap
  • S phase: synthesis
  • G2 phase: second gap
  • G0 phase: resting phase, postmitotic quiescent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is interphase?

A

cell growth and copying of chromosomes in preparation for cell division

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the grey? What is the peach?

A

grey: interphase
peach: mitosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is G1?

A

first gap phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the cell preparing for in G1?

A

entering DNA synthesis phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

T/F: Cell is metabolically active in G1.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does G1 require? What synthesis is occuring?

A
  • Requires nutrients & growth factors
  • RNA, protein, lipid and carbohydrate synthesis occurs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

T/F: No organelles are duplicated in G1

A

False, many are

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How long is G1?

A

variable (6-24 hours)
- short in embryonic and cancer cells
- rapid or non-existent in rapidly dividing cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What phase is DNA and chromosomal protein synthesis occuring?

A

S

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the duration of S phase?

A

approx. 7-8 hours in a typical mammalian cell w/ a 16 hour cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the cell committed to in S phase?

A

cell division

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

T/F: growth factors are needed in S phase

A

False

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What phase does DNA replication occur?

A

S phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is G2 phase?

A

second growth phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What occurs at G2 phase?

A

enzyme, protein, and ATP synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the duration of G2?

A

lasts approximately 3 hours in a typical mammalian cell with a 16-hour cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is M phase?

A

mitotic phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What does the cell undergo during M phase?

A

mitosis and cytokinesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the duration of the M phase?

A

1-2 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

M phase is about _% of the cell cycle

A

10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What state is the cell in in G0 phase?

A

state of withdrawal from cell cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Is the cell dividing or preparing to divide in G0?

A

neither

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the cell doing during G0?

A

Instead, the cell is “doing its job” - performing it’s function within the tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What are examples of cells in G0?

A

hepatocytes, neurons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What type of cell is G0 common in?

A

differentiated cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

In order to progress through the cell cycle, a variety of __ must be turned on.

A

signals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What happens if the environment is not favourable or there are errors in DNA?

A

the cell cycle is “paused” at several main check points (aka “transitions”)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What are checkpoints of the cell based on?

A

series of biochemical switched to initiate a specific cell-cycle events

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is the cell cycle control system?

A

Checkpoints, biochemical switches that decide whether the cell cycle continues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what are features of the biochemical switched?

A
  1. Generally binary (on/off) to launch an event in a complete & irreversible fashion
  2. Robust & reliable
  3. Adaptable & modified to suit specific cell types
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

How are biochemical switched robust & reliable?

A

Contains back up mechanisms to ensure efficacy under variable conditions & if some components fail

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

How are biochemical switched adaptable and modified to suit specific cell types?

A

Responds to specific intracellular or extracellular signals
Cyclin dependent kinases (Cdks)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What are checkpoints (transitions)?

A

Points in the eukaryotic cell division cycle where progress through the cycle can be halted until conditions are suitable for the cell to proceed to the next stage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What are checkpoints regulated by?

A
  • Factors within the cell, mostly controlled by the “health” or “state of preparation” of the cell
  • Factors from outside the cell – i.e. messages from other cells within the same tissue or distant cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Where are the 3 major regulatory transitions?

A
  1. Start Transition (aka G1/S)
  2. G2/M transition
  3. Metaphase-to-anaphase transition (aka M-to-A)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

For most cells, the G1/S seems to be the __-__ and __ step of the cell cycle

A

rate-limiting; committing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Which phase is the rate-limiting and committing step of the cell cycle?

A

G1/S

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

__ __ MUST be present for a cell to pass through the following checkpoints

A

specific signals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

If cell detects problem inside or outside the cell, what happens?

A

it will block progression beyond the checkpoint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

If extracellular conditions are not appropriate for cell proliferation, what happens?

A

central control system blocks progression through the start transition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

If there is a problem with completion of DNA replication, what happens?

A

cell will be held at G2/M checkpoint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

If all the chromosomes are not attached to the spindle, what happens?

A

cell will be held at M phase (metaphase to anaphase)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What are the keys to the cell cycle control system?

A

cyclin-dependent kinases (Cdks)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What are Cdks responsible for?

A

cyclical changes in phosphorylation of intracellular proteins that initiate/regulate the major events of the cell cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What are Cdks controlled by?

A

cyclins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

What do cyclical changes in cyclin protein levels result in?

A

cyclic assembly and activation of cyclin–Cdk complexes at specific stages of the cell cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

What is needed to progess through a checkpoint? What is the exception of this?

A
  • Correct & functional cyclin-cdk complexes
  • Exception: M-to-A checkpoint is a little different
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

What are the 4 different class of cyclins?

A
  1. G1 cyclins: cyclin D
  2. G1/S cyclins: cyclin E
  3. S-cyclins: Cyclin A
  4. M cyclins: Cyclin B
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

What do G1 cyclins (cyclin D) form complex with?

A

Cdk4 or Cdk 6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

What is G1 cyclin (cyclin D) used for?

A

Involved in G1 phase of cell cycle, needed for initiation of transcription of G1/S cyclins to help promote passage through start transition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

What do G1/S cyclins (Cyclin E) form complex with?

A

Cdk2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

What does G1/S cyclins (cyclin E) do?

A
  • Bind Cdk’s at the end of G1 & help trigger progression through start transition
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

When do levels of cyclin E decrease?

A

in S phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

What does S-cyclin (cyclin A) form a complex with?

A

Cdk1 and Cdk2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

What does cyclin A do?

A

Bind Cdks after progression through start transition & helps stimulate chromosome duplication during S phase

contributes to control of some early mitotic events

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

What does Cyclin B form a complex with?

A

Cdk1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

What does cyclin B do?

A

Bind CdKs to stimulate entry into mitosis at the G2/M transition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

When do levels of cyclin B decrease?

A

mid-mitosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

How do cyclin-Cdk complexes work?

A

cyclins function by activating the Cdk

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

How does cyclin protein activate Cdk?

A

directs it to a specific target protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

T/F: A cyclin-CdK complex can induce different effects at different times in the cell cycle

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

Why can cyclin-Cdk complex induce different effects at different times in the cell cycle?

A

Since accessibility of CdK substrates change during the cell cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

Proteins that function in mitosis mat only become available for phosphorylation in what stage?

A

G2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

How does progression through the metaphase-to-anaphase checkpoint occur?

A

via regulated proteolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

What is regulated proteolysis?

A

regulated break down of proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

What is APC/C stand for?

A

anaphase promoting complex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

What is APC/C a family of?

A

ubiquitin ligase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

What is APC/C used for?

A

Used to stimulate proteolytic destruction of specific regulatory proteins
- APC/C polyubiquitinates specific target proteins for destruction in proteasomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

What are target proteins of APC/C?

A

securin, M-cyclins, S-cyclins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

__ __ bind to specific receptors to stimulate cellular growth and proliferation

A

growth factors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

What do growth factors turn on in G1 phase?

A

early response genes and delayed response genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

What do early response genes code for?

A

transcription factors - induce transcription of delayed response genes

78
Q

What do delayed response genes code for?

A

usually Cdks, cyclins, or other proteins needed for cell division

79
Q

In G1, in response to binding of growth factor, what happens?

A

Cyclin D and then E are transcribed and translated and form complexes with their Cdk’s

80
Q

What is the complex of cyclin D and Cdk4 & Cdk6 called?

A

G1-Cdk complex

81
Q

What is the complex of cyclin E and Cdk2 called?

A

G1/S-Cdk complex

82
Q

What allows progression through the G1/S checkpoint?

A

active G1-Cdk and G1/S-Cdk

83
Q

At the G1/S checkpoint, Active G1-cdk (and G1/S-cdk) complex will target a protein called? And do what to it?

A

RB and phosphorylate it

84
Q

How does RB function?

A

transcription co-repressor

85
Q

Hyperphosphorylation of RB will __ RB

A

inactivate

86
Q

What does inactive RB release? What does this cause?

A

transcription factor E2F, allowing transcription to proceed

87
Q

Transcription of cyclin E => G1/S-cdk complex form, does what?

A

promotes passage through the start transition

88
Q

In early S phase, cyclin D (G1-cdk complex) and E (G1/S-cdk complex) are targeted for?

A

destruction

89
Q

What promotes progression through S phase?

A

desruction of cyclin D (G1-cdk complex) and E (G1/S-cdk complex)

90
Q

Active S-cdk complex allows?

A

progression through the S phase of the cell cycle

91
Q

S-Cdk complex levels are still high in?

A

G2

92
Q

M-cyclin levels begin to rise in?

A

G2

93
Q

M-cyclin levels begin to rise in G2 forming?

A

M-Cdk complex

94
Q

What is the M-Cdk complex needed for?

A

to pass through G2/M checkpoint

95
Q

At the end of G2, what is destroyed?

A

S-cyclins

96
Q

How are S-cyclins destroyed?

A

Targeted for proteolysis by APC/C

97
Q

Why do we need to be able to control activity of M-cyclins?

A

so that mitosis doesn’t start too soon

98
Q

Once the M-Cdk complex is assembled, what happens to it immediately?

A

it is inhibited vis phosphorylation

99
Q

When the cell is ready for mitosis to begin, the M-Cdk complex is __-__.

A

de-phosphorylated

100
Q

When can the cell progress through G2/M checkpoint & mitosis begins?

A

once M-Cdk is de-phorphorylated

101
Q

M-cdk complex is needed for?

A

activation of various proteins needed in mitosis

102
Q

Where is the final checkpoint?

A

metaphase-to-anaphase (M-to-A) checkpoint

103
Q

APC/C complex targets a protein called securin by ubiquitylation for?

A

destruction by a proteosome

104
Q

What is securin?

A

an inhibitory protein that protects protein linkages that hold sister-chromatid pairs together in early mitosis

104
Q

What does destruction of securin activate?

A

protease that separates the sister chromatids allowing progression to anaphase

105
Q

At the end of mitosis, M-cyclins are targeted for?

A

destruction by APC/C

105
Q

What does destroying M-cyclins do?

A

inactivates most Cdks in cell

106
Q

When many Cdks in the cell are inactivated at the end of mitosis, what happens?

A

many proteins phosphorylated by Cdks from S phase to early mitosis are dephosphorylated by various phosphatases in the anaphase cell

107
Q

What is required for the completion of M phase, including the telophase and then cytokinesis ?

A

Dephosphorylation of Cdk targets

108
Q

In unfavourable conditions, what happens to the cell cycle?

A

can be paused at any of the main checkpoints

109
Q

When is progression through G1 delayed?

A
  • DNA is damaged by radiation, chemicals, or errors
  • Absence of nutrients or growth factors
  • Abnormal cell size
110
Q

When is entry into M prevented?

A
  • DNA replication is not complete
  • Presence of DNA damage
  • Abnormal cell size
111
Q

When is progression through M-to-A prevented?

A

Chromosomes are not properly attached to mitotic spindle

112
Q

What are two important molecular mechanisms in unfavourable conditions?

A
  • Cdk inhibitory proteins (CKIs)
  • Proteins coded by tumour suppressor genes
113
Q

What does binding of Cdk inhibitory proteins do?

A
  • Inactivates cyclin-Cdk complex
  • stimulate rearrangement in structure of Cdk active site
114
Q

Who are CKI’s primarily used by? What for?

A

used by cells to govern the activities of G1/S- and S-Cdks early in cell cycle

115
Q

What are 3 important CKIs?

A

p16, p21, p27

116
Q

What does p16 inhibit?

A

CyclinD-cdk4 & CyclinD-cdk5 (G1-cdk complex)

117
Q

What does p21 inhibit?

A

CyclinE-cdk2 (G1/S-cdk complex)
CyclinA-cdk2 & CyclinA-cdk1 (S-cdk complex)
Cyclin B-cdk1 (M-cdk complex)

118
Q

What does p27 inhibit?

A

CyclinA-cdk2 & CyclinA-cdk1 (S-cdk complex)
CyclinE-cdk2 (G1/S-cdk complex)
Cyclin B-cdk1 (M-cdk complex

119
Q

What are 2 key tumour suppressor genes?

A

p53, RB

120
Q

What do p53’s do?

A
  • Recognizes and binds damaged DNA
121
Q

Why do unstressed cells have lower levels of p53?

A

since it will be bound by a protein called Mdm2 and be degraded

122
Q

What does RB do?

A
  • recognize damaged DNA
123
Q

What form is RB found in?

A

active form

124
Q

In the presence of DNA damage, __ will be __, releasing __

A

p53; phosphorylated; Mdm2

125
Q

T/F: In the presence of DNA damage, p53 is degraded

A

False

126
Q

Active p53 binds __ and promotes the transcription of __

A

DNA; p21

127
Q

An inactive G1/S-cdk complex will pause the cell cycle at the ____ transition

A

start

128
Q

In the presence of a growth suppressor signal or DNA damage __ is transcribed.

A

p16

129
Q

What does p16 inhibit? What was this needed for?

A

G1-Cdk complex which was needed to inactivated RB

130
Q

Since p16 was transcriped, RB remains activated and bound to __.

A

E2F

131
Q

What does RB bound to E2F cause?

A
  • no transcription of G1/S-cyclins or S-cyclins
  • cell cycle is paused at start transition
132
Q

The cell cycle progression can also be inhibited due to contact with?

A
  • other cells - density-dependent inhibition
  • basement membrane or other matrix component - anchorage dependence
133
Q

What is contact inhibition regulated by?

A

cadherins and beta-catenin

134
Q

What do survival signals promote?

A

the cell cycle and prevent apoptosis

135
Q

What pathway is used by survival signals to promote cell cycle and prevent apoptosis?

A

PI3K-Akt-mTOR C pathway

136
Q

How does Akt in the PI3K-Akt-mTOR C pathway promote cell cycle progression?

A
  • Akt activates/increases:
    Cyclin A –> activation of CDK-1
    Cyclin D –> activation of CDK-4/6
    Akt decreases/inactivates: p21 and p27
137
Q

What is the template for DNA duplication?

A

The DNA double helix acts as a template for its own duplication

138
Q

What will each daughter cell inherit?

A
  • DNA double helix containing 1 original strand and 1 new strand
139
Q

What are the 4 steps of DNA replication?

A
  • strand separation
  • primer creation
  • DNA replication
  • primer removal
140
Q

What bonds help contribute to stability of DNA?

A
  • H-bonds b/w complementary base-pairs
  • Phosphodiester bond within sugar-phosphate backbone
  • Hydrophobic effect due to base-stacking
141
Q

in step 1 (strand separation), what is needed in order for DNA synthesis to begin?

A

DNA double helix must open up

142
Q

What are two proteins are used to open up the double helix?

A
  • DNA helicase
  • single stranded binding proteins
143
Q

What does DNA helicase do?

A

unwinds double helix - breaks H bonds

144
Q

What do single stranded binding proteins do?

A

Bind tightly and cooperatively to stabilize the single strand conformation

145
Q

In step 1 (strand separation), what does opening the double helix create?

A

replication fork

146
Q

What is used at the replication fork to synthesize both new daughter strands of DNA?

A

DNA polymerase

147
Q

What are limitations of DNA polymerase?

A
  • can only add nucleotides
  • only works in 5’ to 3’ direction
148
Q

Why is a primer built in stage 2?

A

DNA polymerase can only add nucleotides to an existing strand of DNA (can only elongate a strand of nucleic acid)

149
Q

What does the primer in stage two serve as?

A

base-paired chain on which to add new nucleotides

150
Q

What is the primary made of in step 2?

A

RNA

151
Q

What makes the primer in stage 2?

A

DNA primase

152
Q

Step 2: Since DNA can only be synthesized in the 5’ to 3’ direction, the replication fork has an __ __

A

asymmetric structure

153
Q

What is the difference between the leading strand and lagging strand in step 2?

A
  • Leading strand: synthesized continuously
  • Lagging strand: synthesized discontinuously. The direction of nucleotide polymerization is opposite to the overall direction of DNA chain growth
154
Q

How many primers are required to start replication on the leading strand?

A

only one

155
Q

How many primers are needed to start replication on the lagging strand?

A

one for each Okazaki fragment

156
Q

What step is when DNA polymerase adds nucleotides in the 5’ to 3’ direction?

A

step 3 - DNA replication

157
Q

In step 4, how are RNA primers removed and replaced with what?

A

by DNA repair system replaced w/ DNA

158
Q

What does DNA ligase do in step 4?

A

joins 3’ end of new DNA fragment w/ 5’ end of previous fragment

159
Q

How does supercoiling occur?

A

As the replication fork moves along the double-strand DNA, anything in front of the replication fork will become overwound forming supercoils.

160
Q

What does DNA topoisomerase do? What does this allow?

A
  • relieves the super-helical tension by breaking the phosphodiester bond
  • allows the two sections of the DNA helix to rotate freely & relieve tension
  • phosphodiester bond will re-form as DNA topoisomerase leaves
161
Q

Why are histones needed in DNA replication?

A

so newly replicated DNA can be packaged into nucelosomes

162
Q

When does histone synthesis occur?

A

during the S phase of the cell cycle

163
Q

What do histone chaperones assist?

A

formation of assembly of histone octomer & nucleosomes

164
Q

Only about _ mistake occurs for every 10^10 nucleotides during DNA replication

A

1

165
Q

What are the DNA proofreading mechanisms?

A
  • DNA polymerase activity
  • exonucleolytic proofreading
  • strand-directed mismatch repair system
166
Q

When does DNA polymerase proofreading activity take place?

A

just prior to a new nucleotide being covalently added to the growing daughter chain

167
Q

How does the DNA polymerase proofreading activity work?

A
  • Correct nucleotide has higher affinity for the DNA polymerase than an incorrect nucleotide
  • So, energetically, incorrectly paired nucleotides are less favourable and therefore more likely to diffuse away before the DNA polymerase can add them by mistake
168
Q

When does exonucleolytic proofreading occur?

A

immediately after an incorrect nucleotide has been covalently added to the growing daughter chain

169
Q

How does exonucleolytic proofreading work?

A
  • An incorrectly added nucleotide will not provide an effective 3’-OH end for DNA polymerase to add on the next nucleotide
  • Separate catalytic site on DNA polymerase will initiate DNA polymerase to move in the 3’ –> 5’ direction, cliping off any unpaired or mispaired residues
  • Catalytic site: 3’-to-5’ proofreading exonuclease
170
Q

What deals with the problem of the lagging strand ending up with a shorter DNA fragment on the daughter strand once the RNA primer has been removed?

A

telomeres

171
Q

What are telomeres?

A
  • Eukaryotes have specialized nucleotide sequences at the end of their chromosomes
  • in humans: many repeats of GGGTTA
172
Q

What are telomere DNA sequences recognized by?

A

telomerase

173
Q

What does telomerase do?

A

replenish telomere sequences each time a cell divides

174
Q

What cells have full telomerase activity?

A

stem cells

175
Q

What cells have low/minimal telomerase activity? Why?

A
  • most cells
  • telomeres gradually shorten until a descendant cell inherits chromosome that lack telomere function
  • Initiates a response causing them to withdraw permanently from the cell cycle and cease dividing - Called replicative cell senescence
176
Q

What is replicative cell senescence?

A

when a cell will cease dividing due to low telomerase activity and telomere function is lacking

177
Q

What does telomerase recognize?

A

the tip of an existing telomere DNA repeat on the parent strand and elongate it in the 5’ to 3’ direction

178
Q

What does telomerase use as a template?

A

a intrinsic RNA template

179
Q

After telomerase is done its job, what happens?

A

DNA polymerase can complete the replication

180
Q

What are the 5 phases of mitosis?

A

Prophase
Prometaphase
Metaphase
Anaphase
Telophase & cytokinesis

181
Q

What is the end-product of mitosis?

A

two identical daughter cells

182
Q

What occurs during prophase?

A
  • Chromosomes condense
  • Since chromosomes have been replicated they consist of 2, closely-associated sister chromatid
  • Mitotic spindles assemble between the two centrosomes
  • Centrosomes have been replicated and are being moved apart
183
Q

What is a centrosome? What does it consist of?

A
  • protein organelle
  • Consists of a pair of centrioles surrounded by a cloud or amorphous material (called pericentriolar matrix)
184
Q

T/F: Centrosomes undergo replication during the cell cycle in preparation for mitosis

A

True

185
Q

What happens during prometaphase?

A
  • Nuclear envelope breaks down
  • Chromosomes attach to spindle microtubules via a protein called a kinetochore
186
Q

What happens during metaphase?

A
  • Chromosomes align at the equator of the cell (halfway between the spindle poles)
  • Kinetochore microtubules attach sister chromatics to opposites poles of the spindle
187
Q

What happens during anaphase?

A
  • Chromatids synchronously separate forming two daughter chromosomes
  • Kinetochore microtubules get shorter while spindle pole moves apart
  • Both these processes contribute to separation of chromosomes
188
Q

What happens during telophase?

A
  • Daughter chromosomes arrive at poles of spindle
  • Chromosomes decondense and a new nuclear envelope reassembles around each set
189
Q

What happens during cytokinesis?

A

Cytoplasm divides in two forming two daughter cells

190
Q

How would you describe the number of chromosomes in each of the following stages of the cell cycle: (n, 2n, 4n, other)
A) G1 of the cell cycle
B) Prophase
C) After cytokinesis

A

A) 2n
B) 2n
C) 2n

BMS 100 Physiology (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions