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Cell Biology > Nucleus, Chromosomes & Chromatin > Flashcards

Nucleus, Chromosomes & Chromatin Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Nuclear envelope

A

double membrane enclosing DNA

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2
Q

Outer nuclear membrane

A

continuous with ER

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3
Q

Inner nuclear membrane

A

carries nuclear specific protein

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4
Q

Nuclear lamina

A

fibrous network that provides structural support to the nucleus

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5
Q

Nuclear pore complexes

A
  • channels through which polar molecules and macromolecules pass through the nuclear envelope
  • large multi-protein complexes with 8-fold symmetry around central channel
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6
Q

Nuclear localisation signal (NLS)

A
  • tag for nuclear protein

- 1 or 2 short sequences with positively charged Lys residues

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7
Q

Nuclear transport receptors

A

Importins - into nucleus

Exportins - out of nucleus

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8
Q

What energy drives nuclear transport?

A

GTP hydrolysis - Ran GTP

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9
Q

Ran-GEF

A

in nucleus

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10
Q

Ran-GAP

A

in cytoplasm

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11
Q

Nucleolus is site of and is a:

A
  • site of ribosome biogenesis

- is an aggregation of rRNA gene clusters

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12
Q

Ribosome structure:

A
  • 2/3 RNA, 1/3 protein

- 1 small & 1 large subunit

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13
Q

rRNA gene organisation

A

tandem arrays

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14
Q

5.8S, 18S and 28S rRNAs transcribed as single:

A

pre-rRNA which is then cleaved to give rise to 3 mature rRNAs

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15
Q

5S rRNA

A

encoded by separate gene

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16
Q

Where are ribosomes assembled and exported to

A

assembled in nucleus and exported into cytoplasm

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17
Q

pre-ribosomal particles

A

exported from nucleus via nuclear pores to yield active ribosomal subunits

18
Q

Compartmentalisation

A
  • transcription in nucleus

- translation in cytoplasm

19
Q

Where do ribosomal proteins assemble

A

on pre-rRNAs in nucleolus

20
Q

Prokaryotic chromosome structure

A

circular with 1 origin of replication

21
Q

E.coli chromosome

A

~ 4.6 million bases encoding 4300 different proteins

22
Q

Eukaryotic genes contain:

A

introns and exons

23
Q

Is there correlation between genome size and evolution?

A

No

24
Q

Eukaryotic chromosome structure

A

linear

25
Q

Interphase nuclei chromosomes

A

distributed throughout nucleoplasm

26
Q

At mitosis chromosomes…

A

condense and can be individually seen with a light microscope

27
Q

3 sequence elements of a functional chromosome

A
  1. telomere
  2. centromere
  3. replication origins
28
Q

DNA replication

A

semi-conservative

29
Q

Telomere function

A

stabilises ends of chromosomes with t-loops

30
Q

Centromere function

A

segregates sister chromatids

31
Q

Rabl configuration

A

centromeres clustered at one end and telomeres at other end of nuclear envelope

32
Q

chromosome organisation in interphase nucleus

A

individual chromosomes occupy a particular region of the nucleus to minimise tangles and help with segregation during mitosis

33
Q

Fundamental unit of chromatin

A

nucleosome

34
Q

Nucleosome core particle

A
  • 147 base pairs of DNA wound around protein core

- protein core made out of histones

35
Q

Octomeric histone core

A

2 molecules of each:

  • H2A
  • H2B
  • H3
  • H4
36
Q

Histone H1

A

linker histone arranges nucleosomes into 30nm fibre

37
Q

2 types of chromatin

A
  • euchromatic

- heterochromatin

38
Q

Euchromatin

A

de-condensed, open and transcriptionally active

39
Q

Heterochromatin

A

condensed, closed and transcriptionally inactive

40
Q

Heterochromatic chromosome regions

A

telomeres & centromeres

41
Q

Histone modification

A

methylation and acylation

42
Q

Epigenetic marks

A
  • genes moved near telomeres can be silences

- X chromosome inactivation

Cell Biology (8 decks)

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