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module 1: cell biology > nucleus, mitosis and meiosis > Flashcards

nucleus, mitosis and meiosis Flashcards

1
Q

What is the nucleus and what does it do

A

Distinguishes eukaryotic and prokaryotic cells

  • Houses genome-genetic info
  • Control centre-replication, transcription, RNA processing
  • Compartmentalisation
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2
Q

describe the structure of the nuclear envelope

A
  • Two nuclear membranes - nuclear lamina and nuclear pore
    complexes
  • Outer and inner membrane acting as a barrier
  • Outer membrane- ribosomes and ER
  • Inner membrane- nuclear proteins
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3
Q

what is the nuclear lamina

A

inner neclear membrane

meshwork of intermediate filaments which bind to inner membrane protiens

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4
Q

what are the 4 different lamins fibrous protiens

A

A, B1, B2, C

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5
Q

what is the function of the nuclear lamina

A

fibrous meshwork provides support

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6
Q

what are the nuclear pore complex

A

channels which small polar molecules, ions and macromolecules travel

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7
Q

what is the transport of molecules in the nuclear pore complex

A

RNA out, transcription factors in

small molecules - passive diffusion
large molecules - energy dependant mechanism

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8
Q

what do histones do

A

they bind to DNA and curls them up into a small peice

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9
Q

what are chromatin

A

complex of DNA and protein

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10
Q

what are the 4 types of chromatin

A
  • Euchromatin- de-condensed and distributed through out the
    nucleus
  • Heterochromatin: 2 types
  • Constitutive never transcribed- satellite sequences of
    centromeres
  • Facultative- not transcribed in these cells
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11
Q

why do cells need to divide

A
  • Development
  • Growth
  • Replacement of cells
  • Wound repair
  • Cancer
  • Sexual reproduction
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12
Q

definition of the cell cycle

A

A cell reproduces by performing an orderly sequence of events in which it duplicates its contents and then divides in two.

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13
Q

what do the checkpoints do in the cell cycle

A

act as breaking mechanism to check chromosome damage

cell cycle can be arrested if not right

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14
Q

what happens at each checkpoint

A

g1 - is environment favourable
g2 - DNA replication and environment
m - chromosomes attached to the spindle

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15
Q

fact

A

cdk controlled by cyclins for protien kinase activity

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16
Q

what is the role of cdk

A

Initiate and control major events of cell cycle- DNA replication,
mitosis and cytokinesis

17
Q

definition of mitosis

A

the division of the nucleus of a eukaryotic cell, involving condensation of the DNA into visible chromosomes, and separation of the duplicated chromosomes to form two identical sets.

18
Q

summary of mitosis

A
  • Chromosome condensation
  • Formation of mitotic spindle
  • Attachment of chromosomes to spindle
  • Sister chromatids separate
  • Move to opposite poles of spindle
  • Formation of new nuclei
19
Q

what happens during propahse

A

replicated chromosomes containing 2 sister chromatids condense. the mitotic spindle assembles between centrosome which have replicated, and move apart

20
Q

what happens during prometaphase

A

breakdown of nuclear envelope, chromosomes attach to spindle microtubules via kinetochores and undergo active movement

21
Q

what happens during metaphase

A

the chromosomes are aligned at equator of spindle, midway between spindle poles. kitetochore microtubules attach sister chromatids to opposite poles of spindle

22
Q

what happens during anaphase

A

sister chromatids synchronously separate to form 2 daughter chromosomes and each are pulled towards each spindle pole.

the kinetochore microtubules get shorter and the spindle poles also move apart.

23
Q

what happens during telophase

A

2 sets of daughter chromosomes arrive at the poles of the spindle and decondense

new nuclear envelope reassembles around each set, completing formation of 2 nuclei and marking end of mitosis

24
Q

what happens during cytokenesis

A

cytoplasm divides in 2 by a contractile ring of actin and myosin filaments, pinching cell in 2 to create 2 daughter cells with a nucleas

25
Q

what controls the dissolution of nuclear envelop - chromosomes condense then reformation of nuclear envelop

A

phosphorylation and dephosphorylation under control of CDK1 and cyclin B

26
Q

What 3 events happen to nucleus during mitosis

A
  • 1) nuclear membrane fragments into vesicles
  • 2) nuclear pore complexes dissociate
  • 3) nuclear lamina depolymerises
27
Q

meiosis definition

A

two successive nuclear divisions
with only one round of DNA replication, which produces four
haploid daughter cells from an initial diploid cell.

28
Q

when can yeast undergo meiosis

A

form spores my meiotic division

29
Q

what does cross over do

A

increases genetic variation

30
Q

what is chromosomal crossover

A

the exchange of genetic material between non-sister chromatids of homologous chromosomes during meiosis, which results in new allelic combinations in the daughter cells

module 1: cell biology (4 decks)

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