Cell division and cell death Flashcards

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1
Q

Cell cycle

A

Consists of interphase and mitotic phase.

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2
Q

Interphase

A

G1 phase: Physical growth (G0 phase: Inactivity).
S phase: DNA replication.
G2 phase: Preparation for division.

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3
Q

Mitotic Phase

A

M phase.
Mitosis
Cytokinesis.

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4
Q

DNA replication

A

After DNA replication each chromosome is made of two identical copies: Sister chromatids.
Two types:
Semi-conservative
Semi-discontinous

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5
Q

Semi-conservative (Exam)

A

As the DNA double helix is unwound by helicase, replication occurs separately on each template strand in antiparallel directions resulting in each copy having 1 parental strand and 1 newly synthetized strand.

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6
Q

Semi-discontinuous (Exam)

A

1 strand is synthetized continuously (leading strand). The other synthetized in fragments, okazaki fragments, (Lagging strand).

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7
Q

How does the DNA replication work?

A

Helicase breaks the hydrogen bonds between the nitrogenous base pairs.
RNA primer produced by RNA primase sticks to the split DNA to start synthesis, extends from 5’ end to 3’ end.
In semi-discontinuous, the strands are replicated in opposite direction. Leading strand is replicated normally while the lagging strand can only replicate fragments (okazaki) at a time, needing multiple primers.
Exonuclease removes the RNA primers.
A specific DNA polymerase fills the gaps.
DNA ligase joins DNA fragments.

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8
Q

Helicase

A

Unwind DNA (exposing template)

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9
Q

Primase

A

Synthetize RNA primer (necessary for DNA polymerase to start)

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10
Q

DNA polymerase

A
Synthesis DNA (5’ -> 3’)
Fills gaps left by RNA primers.
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11
Q

EXONUCLEASE

A

Removes RNA primers

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12
Q

DNA LIGASE

A

Closes the gaps.

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13
Q

Mitosis

A

4 phases:

  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase
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14
Q

What is the purpose of Mitosis?

A

Growth/repair tissue.
Replace worn out cells.
Maintainance of tissue.

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15
Q

What is the results of Mitosis? (Exam)

A

Two genetically identical diploid cells.

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16
Q

Diploid Cell

A

Has two copies of each chromosome. Homologous pair.

17
Q

Chromatids

A

Two sister chromatids make 1 chromosome.

18
Q

Prophase

A
Nuclear envelope disappears.
Chromatin condenses.
Centrosomes migrate to opposite poles.
Formation of mitotic spindle (microtubules).
Chromosomes captured by spindle fibers.
19
Q

Metaphase

A

Chromosomes align at the equatorial plate (metaphase plate).
Bound to microtubules from opposite poles.

20
Q

Anaphase

A

Separation of chromosomes, sister chromatids go on opposite poles.

21
Q

Telophase

A

Nuclear envelope appears
Chromatin decondense
Spindle disappears.

22
Q

Cytokinesis

A

Splitting of the cytoplasm (Microfilaments).

23
Q

What is the difference between mitosis and cytokinesis?

A

Mitosis divides the nuclea.

Cytokinesis divides the cytoplasm.

24
Q

Necrosis

A

Trauma/infection
cells explode
inflammation and tissue damage.

25
Q

What are the two types of cell death?

A

Necrosis and apoptosis

26
Q

Apoptosis

A
Planned
Physiological
No inflammation, no tissue damage.
Cells collapse, break up into fragments called apoptotic bodies that are reabsorbed (phagocytosis).
Triggered in two ways:
Intrinsic pathway
Extrinsic pathway
27
Q

How do cells die in apoptosis?

A

Initiator caspases start proteolytic cascade:
Activating executioner caspases.
Cleavage of structural proteins
Activation of DNA-degrading enzymes

28
Q

Intrinsic pathway

A

Cellular stress/damage
Release of cyt c from mitochondria to cytosol.
Apoptosome assembly.
Activation of initiator caspases.

29
Q

Extrinsic pathway

A

Immune system kills the cell.
Extracellular stimulation of death receptors.
Disc: death inducing signaling complex.
Activation of initiator caspases.