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cytology > nucleus, cell cycle and mitosis > Flashcards

nucleus, cell cycle and mitosis Flashcards

1
Q

diploid population

A
  • 2x deleterious mutations
  • 2x as many selective deaths
  • greater size of mutant population (masked mutations persist for longer time and spread)
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2
Q

structural basis of nucleus

A
  • there is a correlation between geometry of the nucleus and cell shape/dimension important for diagnostic clues
  • DNA as chromosomes
  • double membrane nuclear envelope with pores
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3
Q

chromosomes

A
  • chromosomes
  • chromonema (chromatin fibers)
  • chromatin (DNA + histone complex)
  • DNA (double helix coding segment)
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4
Q

why is DNA tightly packed

A
  • 2.1m total length
  • must be folded and tightly packed
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5
Q

chromatin organisation in interphase cell

A
  • territory model
  • each chromosome occupies a defined volume and only overlaps with its immediate neighbours
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6
Q

hetero vs euchromatin

A
  • h: condensed form
  • eu: dispersed form
  • packing is related to DNA transcriptional activity
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7
Q

nucleosome

A
  • composed of a little less than two turns of DNA wrapped around a set of 8 histone proteins
  • this shortens DNA 7 folds
  • about 200 nucleotide pairs DNA
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8
Q

epigenetic mechanism regulating gene expression

A
  • histone modification: (de)acetylation
  • DNA methylation
  • non-coding RNAs: circRNA, miRNA, lncRNA
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9
Q

nuclear lamina

A
  • meshwork of filaments underlying inner nuclear membrane
  • anchors chromosomes
  • histone methylation anchors the chromosome to the lamina
  • mutation in LMNA gene: cells unstable: precious aging: progeria
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10
Q

cytoskeletal elements in nucleus

A
  • naturally stored actin in an oocyte helps transcriptional reprogramming in a polymerisation dependent manner
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11
Q

nucleoplasm

A
  • karyoplasm
  • nuclear matrix + chromatin granules + riboNucleoprotein particles
  • contains enzymes involved in RNA processing and splicing, ATPases, GTPases, phosphatases, steroid Rs, heat shock proteins…
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12
Q

nuclear envelope

A
  • selective barrier between cytoplasm and nucleus
  • nuclear pore complex: nucleoporin proteins: passive diffusion and energy dependent transport:
  • cytoplasimc ring, central framework with pore, laminal subunit, nuclear basket, terminal ring
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13
Q

why do cells need to divide

A
  • reproduction
  • growth
  • tissue renewal (cell replacement)
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13
Q

nucleolus

A
  • ribosome factory: synthesis and assembly
  • in nucleus w/o membrane
  • highly electron dense
  • nucleolar matrix: nucleolus organising regions: contain several tandem copies of rDNA
  • 200 copies of rRNA genes on 10 ch: needed to keep up with ribosome demand
  • granular component: maturing ribosomal subunits
  • fibrillar center: DNA loops (ch 13,14,15,21,22) not being in ts
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14
Q

ribosome assembly

A
  • ribosomal proteins enter nucleolus
  • pre-rRNA from rDNA combines with proteins
  • preribosomal particles, 5S rRNA to 60s subunit, 40s subunit
  • transported out
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14
Q

how to asses cell cycle

A
14
Q

cell cycle

A
  • prepares for division
  • most time is G1 and S phases
  • G1: organelle duplication, normal functions
  • G2: one or more nucleoli, two centromeres, uncondensed chromosomes
15
Q

structure of metaphase chromosome

A
  • microtubules attached to kinetochore at centromere
  • cohesins: protein complex that mediates sister chromatid cohesion, homologous recombination, and DNA looping
  • centromere: specific sequence binds to 2 discs of protein (kinetichores)
16
Q

mitosis

A
  • prophase: ch condensation, mitotic spindle (cytoskeleton) reorganisation, nucleolus and envelope disappearance
  • chromosomes free from anchorage in pro-metaphase (lamins phosphorylated)
  • metaphase: h anchoring to microtubules, alignment at equator of spindle
  • anaphase: spindle elongation, cohesins degradation, sisters separate and migrate toward poles
  • telophase: spindle degradation, reconstruction of nucleus and nucleolus, chromosome unwinding, cytokinesis
17
Q

the human karyotype

A
  • ordered visual representation
  • analysis of numbers and abnormalities
  • photographed when highly condensed, arranged in order of decreasing size
  • 44 autosomes + 2 sex chromosomes
18
Q

cell cycle regulation

A
  • cell cycle entry: intrinsic factors (TS, cycle regulators) and extrinsic factors (ROS, hypoxia, TPO, SCF)
  • quiescence entry: G0: senescence: intrinsic and extrinsic factors
  • restriction point
  • cell cycle tightly regulated: defects result in hyperplasia and cancer
19
Q

cell cycle checkpoints

A
  • G1
  • G2
  • M
  • ensures cell cycle proceeds without errors
  • errol nézz majd egy videót
19
Q

hallmark capabilities of cancer

A
  • sustaining proliferative signalling
  • evading growth suppressors
  • activating invasion and metastasis
  • enabling replicative immortality
  • inducing angiogenesis
  • resisting cell death

cytology (7 decks)

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