bio 151 exam 2 Questions And Answers
A
R
U
LA
C
O
D
,reasons why cells divide (3) - ANS growth
repair
A
reproduction
cell cycle (order of specific phases) - ANS interphase, prophase, prometaphase,
R
metaphase, anaphase, telophase and cytokinesis
what happens in mitosis - ANS -nuclear envelope
division and cytokenesis
S U
interphase phases - ANS G1
LA
G2
what is happening in G1? - ANS growing, making more organelles
checkpoint of G1 - ANS G1/S
C
G2 - ANS protein synthesis and preparation for division, check to make sure DNA is
replicated
checkpoint of G2 - ANS G2/M
O
what is happening in S phase - ANS DNA replication (dna duplicated) at the end the cell
has twice as much
D
checkpoint of S phase - ANS none
M phase - ANS mitosis (nuclear division)
cytokinesis (cytoplasmic division)
checkpoint of M phase - ANS m
reasons why the cell cycle must be tightly regulated (4) - ANS 1. too much division gives
cells when the organism does not need them
, 2. not enough division means no cells when the organism needs them
3. dividing too early and there might be problems with DNA
4. entering anaphase too early could mean nbiorientation not achieved and could get
aneuploidy (presence of an abnormal number of chromosomes in a cell)
what is being checked at the G1/S checkpoint - ANS DNA damage checkpoint: (occurs
before entering S phase) Is DNA damaged?
what is being checked at the G2/M checkpoint? - ANS DNA replication checkpoint: (at the
end of G2) Is all DNA replicated?
A
what is being checked at the M checkpoint? - ANS spindle checkpoint (before anaphase):
are all chromosomes attached to the spindle
R
what is significant about the "start" (G1/S) checkpoint ? - ANS cells are committed to divide
or die
what controls the checkpoints? what are the concentrations of these proteins throughout the cell
U
cycle? - ANS active cyclin/CDK complexes
CDK levels stable; cyclin levels vary
LA
what is the role of Rb - ANS "check" inhibits E2F
what is the role of E2F? - ANS turns transcription on--> progress into cycle
what stops the cell cycle from processing? what drives it - ANS Rb, "gas pedals" E2F and
cyclin/CDK
C
explain diagram with DNA damage - ANS -start checkpoint
-when DNA damage detected --> activates p53
-p53 activates p21
O
-p21 inhibit CDK/cylcin
explain diagram with pRb - ANS Rb inhibiting E2F
D
CDK/cyclin phosphorylate Rb
Phosphorylated Rb releases E2F
E2F leads to cell cycle progression
Occurs at each checkpoint
what stops the cell cycle from progressing? - ANS Rb "checks"
what drives the cycle cycle? - ANS E2F & cyclin/CDK "gas pedals"
what checkpoint does DNA damage occur in? why? what is the role of p21? - ANS G1/S
A
R
U
LA
C
O
D
,reasons why cells divide (3) - ANS growth
repair
A
reproduction
cell cycle (order of specific phases) - ANS interphase, prophase, prometaphase,
R
metaphase, anaphase, telophase and cytokinesis
what happens in mitosis - ANS -nuclear envelope
division and cytokenesis
S U
interphase phases - ANS G1
LA
G2
what is happening in G1? - ANS growing, making more organelles
checkpoint of G1 - ANS G1/S
C
G2 - ANS protein synthesis and preparation for division, check to make sure DNA is
replicated
checkpoint of G2 - ANS G2/M
O
what is happening in S phase - ANS DNA replication (dna duplicated) at the end the cell
has twice as much
D
checkpoint of S phase - ANS none
M phase - ANS mitosis (nuclear division)
cytokinesis (cytoplasmic division)
checkpoint of M phase - ANS m
reasons why the cell cycle must be tightly regulated (4) - ANS 1. too much division gives
cells when the organism does not need them
, 2. not enough division means no cells when the organism needs them
3. dividing too early and there might be problems with DNA
4. entering anaphase too early could mean nbiorientation not achieved and could get
aneuploidy (presence of an abnormal number of chromosomes in a cell)
what is being checked at the G1/S checkpoint - ANS DNA damage checkpoint: (occurs
before entering S phase) Is DNA damaged?
what is being checked at the G2/M checkpoint? - ANS DNA replication checkpoint: (at the
end of G2) Is all DNA replicated?
A
what is being checked at the M checkpoint? - ANS spindle checkpoint (before anaphase):
are all chromosomes attached to the spindle
R
what is significant about the "start" (G1/S) checkpoint ? - ANS cells are committed to divide
or die
what controls the checkpoints? what are the concentrations of these proteins throughout the cell
U
cycle? - ANS active cyclin/CDK complexes
CDK levels stable; cyclin levels vary
LA
what is the role of Rb - ANS "check" inhibits E2F
what is the role of E2F? - ANS turns transcription on--> progress into cycle
what stops the cell cycle from processing? what drives it - ANS Rb, "gas pedals" E2F and
cyclin/CDK
C
explain diagram with DNA damage - ANS -start checkpoint
-when DNA damage detected --> activates p53
-p53 activates p21
O
-p21 inhibit CDK/cylcin
explain diagram with pRb - ANS Rb inhibiting E2F
D
CDK/cyclin phosphorylate Rb
Phosphorylated Rb releases E2F
E2F leads to cell cycle progression
Occurs at each checkpoint
what stops the cell cycle from progressing? - ANS Rb "checks"
what drives the cycle cycle? - ANS E2F & cyclin/CDK "gas pedals"
what checkpoint does DNA damage occur in? why? what is the role of p21? - ANS G1/S
