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Fundamentals Of The Living Cell > The cell cycle > Flashcards

The cell cycle Flashcards

1
Q

What are duplicated in the cell cycle and divided into?

A

DNA, organelles, cytoplasm

and divided into daughter cells

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2
Q

How many organisms does the cell cycle give rise to?

A

2 new organisms

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3
Q

What must the zygote undergo?

A

A zygote must undergo many rounds of the cell cycle to make a new fully grown organism

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4
Q

What must multicellular organisms like humans fo during their lifetime?

A

Must also constantly replace any cells that die during the lifetime of the organism

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5
Q

What is not possible with nerve cells

A

Nerve cells cell cycle re-entry is not possible

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6
Q

What happens to hepatocytes in the cell cycle?

A

Maintained in G0 unless stimulated to divide

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7
Q

What are epithelial and haematopoietic cells in?

A

Constantly in the cell cycle

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8
Q

What does FACS analysis show regarding DNA content during the cell cycle?

A

FACS analysis allows us to see that DNA content is greatest during the G1 phase and the lowest during the S phase

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9
Q

G1

A

Growth and preparation for S phase

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10
Q

S

A

Chromosome duplication

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11
Q

G2

A

Growth and preparation for M phase

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12
Q

what steps is interphase made up of?

A

G1+S+G2

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13
Q

What steps is the M phase made up of?

A

Made up of Mitosis and cytokenesis

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14
Q

Prophase

A

Chromosomes condense
Centrosomes move to opposite poles
Mitotic spindles form

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15
Q

Prometaphase

A

Nuclear envelope breakdown

Chromosomes attach to the mitotic spindle

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16
Q

Metaphase

A

Centrosomes are at opposite poles

Chromosomes are at there most condensed and line up at the equator of mitotic spindle

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17
Q

Anaphase

A

Sister chromatids separate

Each new daughter chromosome move to opposite spindle pole

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18
Q

Telophase

A

Chromosomes arrive at the spindle poles
These chromosomes expand
Nuclear envelope forms

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19
Q

What occurs in Cytokenesis?

A

Cytoplasm divides

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20
Q

What is the mitotic spindle?

A

Bipolar array of microtubules

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21
Q

When do mitotic spindles start assembling and from where?

A

Start assembling during prophase from the centrosomes at each pole

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22
Q

How do mitotic spindle attach to chromosome?

A

Attach to the chromosomes via the kinetochore

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23
Q

What do mitotic spindles do

A

Pull apart the sister chromatids

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24
Q

What are the 3 types of spindle fibres

A

Astral microtubules
Kinetochore microtubules
Interpolar microtubules

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25
What is the Kinetochore?
A protein structure formed on a chromatid, where the spindle fibres attach and pull the chromatids apart during cell division
26
What is the centromere?
a part of the chromosome connected to the spindle fibre
27
What are chromatids?
the two chromosomes that have been replicated and linked through the centromere
28
What organising centre is there in somatic animal cells?
In somatic cells, microtubule organising centre is present
29
What do centrosomes consist of and what is it surrounded by?
Centrosomes consists of a pair of centrioles surrounded by pericentriolar matrix
30
When are centrioles replicated?
Replicated during interphase
31
What do centrioles do to prepare for M phase?
Migrate to opposite poles in preparation for M phase
32
What stage is cytokenesis in the cell cycle?
Final step in the cell cycle
33
What does cytokinesis do?
Divides the cytoplasm into two daughter cells
34
What is the contractile rings structure?
Cytoskeletal structure composed of actin and myosin bundles
35
Where do the actin and myosin bundles in contractile rings accumulate?
Accumulate between the poles of the mitotic spindle beneath the plasma membrane
36
What does the contractile ring do and form?
Ring contracts and forms an indentation or cleavage furrow, dividing the cell in two
37
How do cell organelles regenerate?
Cell organelles spontaneously regenerate so must be already present in the new daughter cells.
38
Mitosis overview
§ Two cells § Diploid § Cells divide once § No recombination between homologous chromosomes
39
Meiosis overview
§ Four cells § Haploid § Cell divide twice Homologous recombination occurs
40
What does meiosis start and end with?
Division which starts with one diploid cell and ends with 4 haploid cells
41
What does meiosis produce
Sperm and Egg cell
42
Steps of mitosis
○ First there's a round of DNA replication during the S phase to double the genetic content ○ Meiosis one: § Homologous chromosomes line up on the spindle and then separate to opposite spindle poles ○ Meiosis two: § Sister chromatids line up on the spindle and separate to opposite spindle pole Recombination occurs between homologous chromosomes
43
What is Nondisjunction?
Failure of homologous chromosomes to separate from one another either at meiotic division one or meiotic division 2.
44
What happens when non-disjuncton occurs in autosomes?
``` § If in autosomes, usually fatal however there are a few exceptions: Trisomy 21(Downs syndrome) ```
45
What happens when nondisjuntion occurs in sex chromosomes?
XO(turners syndrome)
46
What regulation of the cell cycle is required?
○ Entry into the cell cycle must be strictly controlled ○ Each phase must only occur only once per cycle Phases must be in the correct order and non overlapping
47
What are the G1 checkpoints in the cell cycle?
``` § Check extracellular environment, growth factors, mitogenic signals and check for DNA for damage § Induction/expression of cyclin D § Binding/activation of Cdk4 § Phosphorylation of pRB § Release and activation of E2F ``` S phase gene transcription
48
How is DNA damage repaired?
□ Normal p53 degrades very quickly, is unstable and maintained at very low levels □ Phosphorylated p53 is not degraded □ Active p53 promotes the transcription of the p21 gene that induce cell cycle arrest by binding to the promoter region of p21 □ P21 binds and inhibits G1/S-Cdk and S-Cdk complexes Causing cell cycle arrest which gives more time to repair damaged DNA
49
What are the G2 checkpoints in the cell cycle?
Check DNA replicated properly, check for DNA damage
50
What are the metaphase checkpoint?
Are all chromosomes aligned on the mitotic spindle
51
What are the two main cell cycle regulators?
Cdks and cyclins
52
How do Cdks regulate cell cycle?
§ Enzymes which phosphorylate the target proteins Become active when bound to a corresponding cyclin
53
How do cyclins regulate cell cycle?
§ Regulators of Cdks | § Different cyclins are produced at each phase of the cell cycle
54
What are the levels of cdks and cyclin throughout the cell cycle?
Cdk levels fairly stable | Cyclin levels vary
55
What does cdk bound to cyclin do?
Cdk bound to cyclin is active and can phosphorylate target protein
56
What does cdk activation trigger?
Cdk activation triggers the next step in the cell cycle such as entry into S phase or M phase
57
What does Cyclin degradation do?
Cyclin degradation terminates Cdk activity
58
Give two examples of cyclin dependant kinase inhibitors
INK4 and CDK inhibitory protein
59
What does INK4 do
Inhibits G1 CDK's
60
What do CDK inhibitory proteins do?
Inhibit all other CDK-cyclin complexes gradually sequestered by G1 CDKs thus allowing activation of later CDKs.

Fundamentals Of The Living Cell (31 decks)

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