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Cell biology > Cell cycle > Flashcards

Cell cycle Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is meant by “cells arise from pre-existing cells”

A

Part of classical cell theory. Mitosis. DNA from parental strand.

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2
Q

Define cell-cycle and cell-division.

A

(1) to grow and to duplicate the DNA in the
chromosomes
(2) to segregate the DNA
(3) division: 2 identical daughter cells with each a
complete copy of the genome

Cell cycle consists of four phases: G1, S, G2, M

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3
Q

Why are cyclins among the most important cell cycle regulators?

A

Concentrations of cyclins vary in a cyclical way during the cell cycle, and triggers different transition steps in cell cycle.

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4
Q

Describe how the Cdk-complex works

A

Cyclin, a regulatory protein, needs to bind to cyclin dependent kinase (Cdk), forms a complex that phosphorylates proteins and trigger transition steps in cell cycle. Acts as an on/off switch to control cell cycle.

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5
Q

Name the stages of a cell-cycle (in chronological order).

A 
G1, S phase, G2 (interphase) 
M phase (consists of prophase, prometaphase, metaphase, anaphase, telophase and then cytokinesis)
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6
Q

Give 3 functions of the G1 phase

A

Cell growth, synthesis of organelles, lipids and lipids. Prepare to replicate DNA.

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7
Q

What are mitogens?

A

Growth factor that bind to receptors to signal about starting mitosis

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8
Q

What is the function of p53 protein? Describe shortly its working mechanism.

A

DNA damage can stop cell cycle. P53 is a transcription regulator that ensures DNA is not damaged before cycle continues. P53 is needed to activate p21 gene that will allow for mRNA to be produced. If DNA damaged P53 is degraded and does not activate p21 necessary for continuation.

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9
Q

What are the stages of the M-phase, mitosis?

A 
Prophase 
Prometaphase 
Metaphase
Anaphase 
Telophase  
       Cytokinesis
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10
Q

Why is the mitotic spindle a dynamic structure?

A

array of microtubuli formed at the opposite poles of a
cell during mitosis and pulls duplicated chromosome sets apart, must be able to align chromosomes correctly and pull them apart.

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11
Q

Define kinetochore microtubuli

A

protein complex that assembles on the centromere of a condensed
chromosome
A human kinetochore binds 20-40 microtubule

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12
Q

Mitotic spindle with its 3 types of microtubuli during the prometaphase of the
mitosis

A 
Interpolar microtubuli:
“interacting microtubuli”, motor
protein help to cross-link the 2
sets of microtubule
Astral microtubuli: grow towards the cell membrane, contribute to cell stability
Kinetochore microtubules
spindle pole
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13
Q

Define metaphaseplate.

A

The metaphase plate is the plane on which chromosomes align themselves during metaphase

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14
Q

What is the main function of cohesion rings?

A

Two copies of DNA remain tightly bound together
by cohesin rings, which is crucial for proper
chromosome segregation

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15
Q

What is the name given to the division of the cytoplasm at the end of mitosis? Describe the
process.

A

Cytokinesis:
Overlapping interpolar microtubuli of the
mitotic spindle recruit proteins to start
creating a contractile ring
• Position of the contractile ring ensures
equally division
• Contractile ring composed of actin and
myosin filaments

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16
Q

Describe 2 types of cell death.

A 
APOPTOSIS = programmed cell
death
The cell breaks apart into
apoptotic bodies by caspase
pathway –phagocytosis
NECROSIS
Plasma membrane rupture,
nuclear and cellular lysis causes
inflammation
17
Q

What is cancer?

A

Mutations in components of cell-signalling pathway (own
extracellular survival signals, Ras)
•Mutations in genes responsible for cell death (p53→
G1/S-Cdk and S-Cdk)
•Uncontrolled cell proliferation
•Overactive cell metabolism
•Invasive due to lack of adhesion molecules
•Survival and proliferation in abnormal locations

18
Q

Why is cancer fundamentally a genetic disease?

A 
defects in DNA replication
defects in DNA repair
defects in cell-cycle checkpoint mechanisms
mistakes in mitosis
abnormal chromosome numbers
genetic instability
predisposes the cell to malignant
transformation
19
Q

Define proto-oncogen and tumor-suppressor gene.

A

Normal gene induce normal cell proliferation
Mutation in proto-oncogene creates oncogene which
accelerates cell growth and division
Act in dominant manner

20
Q

What is the prometaphase?

A 
Chromosomes attach to the mitotic spindle via kinetochores
\+ active movement (chromosome)
- Breakdown of nuclear envelope
- Kinetochore microtubuli attach to
kinetochores
- Interpolar microtubuli move the
centrosome to opposite directions
21
Q

What happens in the anaphase?

A

Sister chromatids split synchronously and are pulled to the opposite
ends of the cell
chromosome segregation by motor proteins dynein and kinesin.
Cohesin rings around the chromatids destroyed by separase (= first
step of the anaphase)

22
Q

What happens during metaphase?

A

Chromosomes line up to the centre of the cell (equator) and form
the metaphase plate
The kinetochore microtubules pull the sister chromatids back
and forth until they align along the centre of the cell

23
Q

What happens during telophase?

A

Disassembly of mitotic spindle
• Re-assembly of a new nuclear envelope around each set of chromosomes →
2 daughter nuclei
• decondensation of chromosomes →gene transcription possible
• Mitosis is complete at the end of the telophase

24
Q

What is the mitotic spindle?

A

array of microtubuli formed at the opposite poles of a

cell during mitosis and pulls duplicated chromosome sets apart. must be able to form two, move and pull

25
Q

What are the different stages of cancer development?

A

HYPERPLASIA: an increase in the number of cells in
an organ or tissue. Normal appearance. They are
not cancer, but may become cancer.
DYSPLASIA: Abnormal appearance of cell (shape,
size, pigmentation…)
IN SITU CARCINOMA/NEOPLASM: a group a
abnormal cells that remain in the place where they
were formed –cancer
INVASIVE CANCER: a cancer which has invaded
beyond the membrane and has potential to spread
to other parts of the body →metastases

26
Q

What are the three types of cells?

A

Labile (proliferative)
Stable (replicate when stimulus for it)
Permament cells (do not undergo mitosis)

27
Q

What happens in the first phase of the cell cycle, G1?

A

Cells get ready to replicate by increasing number of organelles, synthesise proteins and enzymes for DNA replication
Repair thymidine dimers

28
Q

What happens in the S phase, synthetic phase of the cell cycle?

A

Replicate genetic material from 46 to 92 chromosomes.

Takes around 6 hours.

29
Q

What happens in the G2 phase of cell cycle?

A

Cell grown in size, increasing cytoplasm and different components in the cell

30
Q

What is G1, S phase and G2 also referred to as?

A

Interphase

31
Q

What happens during the M phase? (Mitosis phase)

A

Prophase
Metaphase
Anaphase
Telophase

Cell biology (11 decks)

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