Brainscape's Knowledge GenomeTM

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


See full index

BIOL 200 > Unit 7 > Flashcards

Unit 7 Flashcards

1
Q

Cell cycle

A

A continuous and discrete process. Discrete (discontinuous) processes only occur at certain points in the cycle (ex. DNA rep., mitosis). Continuous processes occur throughout the cell cycle (ex. nutrient assimilation, cell growth). Cell cycle checkpoints combine continuous (like growth) and discrete processes (DNA rep.), so cell size is maintained

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

Why do the duration of the cell cycle differ in different cells

A

Some cells can be arrested in G1 (also called G0). This can be temporary or permanent. It is where the cell decides if it should divide or stop

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

G1 phase

A

Major period for cell growth where organelles duplicate and the volume of the cyto inc.

Ends at the G1/S checkpoint where it can continue or stop at G1 (called G0)

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

Cell transition through the stages (G1 - S)

A

It is highly regulated. It is controlled by specific proteins in the cyto. When they are not present, the cell will stay in G1 (G0). The cell will continue to S only if the end goal is division

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

Synthesis (S-phase)

A

DNA replication occurs and chromosome duplication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

DNA replication in S-phase

A

There are multiple origins of replication throughout the chromosome which have bidirectional movement of replication forks away from the origin of rep.

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

DNA synthesis is semi-conservative

A

Each replicated double helix consists of one conserved (parental) DNA strand and one newly synthesized DNA strand

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

G2 phase

A

Third phase in interphase. Cell continues to grow in prep for mitosis. Phase is shorter than G1. Ends with G2/M checkpoint (ie. commitment to divide). Checkpoint can repair DNA, and if it cannot be repaired, it will be destroyed or cancer may occur

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

M-phase

A

Mitosis occurs (nuclear division), where the replicated chromosomes (sister chromatids) condense to facilitate separation by mitotic spindle. Then cytokinesis (cytoplasm division) occurs, where the cell divides itself into two genetically identical daughter cells

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

Fluorescence-Activated Cell Sorting (FACS)

A

Cells are stained with a dye that fluoresces upon binding DNA and the amount of DNA is proportional to the amount of fluorescence emitted. The cell sorter measures and separates cells with different fluorescence, which indicates different amounts of DNA

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

Cell cycle checkpoints

A

Regulate the cell cycle by monitoring that all the steps in the previous phases have been correctly done before continuing. If conditions are not met, it will stall until they are

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

G1/S checkpoint

A

Is the cell large enough? Are nutrients available? Is the DNA intact?

Otherwise, cell is arrested in G0

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

G2/M checkpoint

A

DNA replication complete? DNA undamaged? Cell large enough?

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

Mitosis checkpoint

A

Are replicated chromos properly attached to mitotic spindle?

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

What would happen if the Gap phases were eliminated from the cell cycle?

A

Smaller daughter cells would result after cell division

Example of this are from embryonic cells, which skip the gap phases and go straight to mitosis after duplicating their DNA

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

Why would a cell injecting with the cytoplasm of an M-phase cell go into mitosis, but injecting a cell with the cytoplasm from an interphase cell will not?

A

M-phase has factors that control oocyte entry into M-phase called a maturation promoting factor (MPF), which is a positive regulator, meaning its presence makes mitosis occur

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

How does MPF initiate mitosis?

A

It contains a kinase, which is an enzyme that phosphorylates target proteins using ATP. This phos/dephos result in conformational changes that activate/deactivate the target protein

18
Q

MPF kinase presence and activity throughout the cell cycle

A

Always present, but its activity oscillates. It is turned on and off via cyclin, which binds to MPF kinase and regulates its activity. Cyclin accumulates during interphase, maxes in mitosis, then rapidly declines at the end of mitosis, therefore, MPF follows this pattern

19
Q

Cyclin-dependent kinase (Cdk)

A

This is still MPF kinase, but describes how it needs cyclin to be activated

20
Q

How is the activity of M-Cdk regulated?

A

Cdk/cyclin activity is degraded during mitosis anaphase and turns it off. It’s initially tagged by ubiquitin, which signals a degradation by the proteasome

21
Q

Why do cells injected with the cytoplasm from a cell in M-phase initiate DNA synthesis?

A

A factor controls entry into S-phase, which is a +ve regulator of the cell cycle

22
Q

The function of Cdks and cyclins

A

They control the different checkpoints of the cycle (ie. entry into S-phase and M-phase)

23
Q

S-Cdk and M-Cdk

A

Active S-Cdk triggers DNA rep. and controls mechanisms to ensure DNA is fully replicated only once

Active M-Cdk triggers entry to mitosis

24
Q

Is the binding to Cdk to cyclin necessary and sufficient to activate the complex?

A

No - its binding changes the config of the active site of Cdk and only makes it possible to be active, but does not activate enzyme activity

25
Q

2 processes of turning on Cdk enzymatic activity

A

1) Association with cyclin

2) Phos/dephos of cyclin/Cdk complex (which controls activation)

26
Q

What does lost of fxn (LoF) and gain of fxn (GoF) of fission yeast tell us about the phos/dephos of cyclin/Cdk complex

A

LoF, the amount of wild-type enzyme is reduced, therefore, the cells grew very large. GoF, the amount of wild-type enzyme is increased, therefore, the cells divide quickly and results in small cells

27
Q

4 steps of M-Cdk activation

A

1) M-Cdk and Cyclin bind, M-Cdk is inactive
2) Inhibitory phosphorylation
3) Activating phosphorylation
4) Removal of inhibiting phosphate

Note: inhibitory phosphate trumps activating phosphate. Inhibitory kinase (Wee1) adds the inhibitory phosphate on the complex. Activating kinase (Cak) adds activating phosphate. Activating phosphatase (Cdc-25) removes the inhibitory phosphate and makes the complex active

28
Q

How does activated M-Cdk indirectly activate more M-Cdk?

A

Active M-Cdk phosphorylated Cdc-25 phosphatase (when they remove the inhibitory phosphate) to turn it on. Causes a +ve feedback loop where the initial amounts of CdC-25 will lead to higher levels of Cdc-25 activity and a rise in M-Cdk activity. This leads to drive cells into mitosis if all conditions at the G2/M checkpoint have been met

29
Q

How would an indestructible M-cyclin affect the cell cycle?

A

This will block entry to G1. The separation of chromosomes will still occur because the inactivation/destruction of cyclin will not happen before the separation of the rings(?), so separation will still happen

30
Q

3 tasks that must occur before M-phase begins

A

1) Centrosome duplication - triggered by S-Cdk. Centrosomes duplicate
2) DNA replication - in S-phase, cohesin ring proteins hold the replicated chromatids together, which will be degraded in anaphase after chromosomes are attached to the spindle
3) Organelle duplication and cell size increases - occurs in G2

31
Q

M-phase 2 stages

A

1) Mitosis (nuclear division - 5 stages)

2) Cytokinesis (cytoplasmic division)

32
Q

1) Prophase

A

Triggered by M-Cdk activation by Cdc-25. M-Cdk phosphorylates histone H1, codensins (further packages interphase chromatin), microtubule-associated proteins, nucleolins, and nuclear pore proteins and lamins. This combined phosphorylation allows chromosomes to condense, mitotic spindles form (they are shorter and more dynamic at this stage) and migrate, nucleolus disintegrates, and nuclear lamina breaks down

33
Q

Interpolar MTs

A

A bridge formed when 2 MTs interact. Motor proteins and other MT associated proteins help stabilize interpolar MTs

34
Q

2) Prometaphase

A

Nuclear env breaks down into small vesicles and the chromosomes are fully condensed. Kinetochores have formed at the centromeres and the + end of the MTs bind to the chromosomes at kinetochore

35
Q

3) Metaphase

A

Chromosomes are aligned at the metaphase plate, the equator of the cell

36
Q

3 types of MTs

A

1) Astral MTs
2) Kinetochore MTs
3) Interpolar MTs

37
Q

How are MTs attached to the kinetochore?

A

It has been observed that when a low [tubulin] is added, it is added onto the spindle in small amounts towards the pole with no change in length. This occurs through treadmilling, and the kinetochore has a protein collar that connects to the MT and allows treadmilling. There is a gain of subunits in one MT and the loss on the other, which allows the chromosomes to align at the metaphase plate

38
Q

4) Anaphase

A

Sister chromatids synchronously separate, triggered by M-Cdk phosphorylation of APC (anaphase promoting complex) and cohesins degrade. Kinetochore MTs get shorter (anaphase A). Interpolar MTs lengthen and astral MTs shorten, pulling poles apart. Kinesins and dynein help (anaphase B)

39
Q

Activation of APC by M-Cdk-mediated phosphorylation triggers degradation of cohesins, allowing chromosomes to separate. Its activation also allows the ubiquination of M-cyclin and targets the M-cyclin for degradation via proteasome

A

idc anymore. Lecture 36 slide 35

40
Q

5) Telophase

A

Controlled by the destruction of M-cyclin. The nuclear envelope re-assembles around each set of chromosomes and two nuclei form. Spindle fibers disappear and division of cytoplasm begins and contractile ring assembles

41
Q

Cytokinesis in animal cells

A

Cytoplasm splits into two and cell divides into two daughter cells due to contraction of actin/myosin ring

42
Q

Cytokinesis in plant cells

A

Division of cytoplasm is guided by a MT-based structure called the phragmoplast. New cell wall forms and divides the plant cell

BIOL 200 (7 decks)

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