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BL2301 Cell Biology > The Nucleus > Flashcards

The Nucleus Flashcards

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1
Q

What are the 4 main functions of the cell nucleus?

A
  • Stores genomic DNA
  • Replicates genomic DNA once every cell cycle
  • Controls expression of the genome
  • Communicates with the cytoplasm
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2
Q

Why does the eukaryotic cell have a more complex protein synthesis?

A
  • As it involves splicing pre-mRNA to remove introns using splicing factors before exit through the nuclear pore
  • Prokaryotic cells simply have transcription and translation
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3
Q

What is the importance of the cell nucleus in embryonic stem cells?

A

Allows cell to differentiate into different cell types, with interactions between the nuclear structure and the sub-nuclear domains being vital for correct and efficient gene expression

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4
Q

Name 3 human diseases linked to the cell nucleus

A
  1. Leukaemia
  2. CAG triplet diseases
  3. Laminopathies
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5
Q

What are 2 observed traits of chromosomes?

A
  • Occupy distinct territories

- Different levels of chromatin condensation

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6
Q

What are the main functions of the nucleolus?

A
  • Makes ribosomes

- Composed of the fibrillar centre where genes encoding for ribosomal RNA are found

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7
Q

What is the role of the dense fibrillar component?

A

rRNA processing

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8
Q

What is the role of the granular component?

A

assembly of ribosome subunits

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9
Q

What are nuclear speckles and what are their function?

A
  • Contain protein splicing factors such as snRNP and non-snRNP
  • Acts as storage site for splicing factors that proteins can move in and out of (shown by photobleaching)
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10
Q

What are nuclear bodies?

A

A variety of structures found in the nucleus that tend to be spherical and which have various roles in gene expression

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11
Q

Give 3 examples of nuclear bodies and their functions

A
  1. PML bodies are involved in transcriptional regulation
  2. Cleavage bodies are involved in the formation of the 3’ of mRNA
  3. Cajal bodies & gems are involved in the synthesis of snRNP and splicing factors
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12
Q

What is the nuclear pore complex?

A

Found on the nucleus side of the nuclear pores, with each one being formed of 8 subunits

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13
Q

What is the function of the nuclear lamina?

A

Provides support to the nuclear envelope by binding/anchoring to membrane proteins, lipids (by insertion and modification) and the nuclear pore complex

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14
Q

What are mutations in Lamin A associated with?

A

Hitchinson-Gilford progeria which causes premature aging

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15
Q

Name 5 things that travel in and out of the nucleus

A
  1. Protein
  2. RNA
  3. Glucose
  4. ATP
  5. Ions
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16
Q

What do the rates of nuclear passage depend on?

A

Protein complexity

17
Q

What are the 2 categories of karyopherins?

A

importins and exportins

18
Q

Where are RanGTP/RanGDP (Ras-related nuclear protein) usually found?

A

RanGDP - cytosol

RanGTP - nucleus

19
Q

How does RanGTP/GDP control nuclear transport?

A

By a carefully maintained nuclear gradient

20
Q

How is the RanGTP/GDP gradient maintained?

A

Ran-GAP protein in the cytosol dephosphorylates RanGTP to form RanGDP
Ran-GEF in the nucleus which is attached to chromatin phosphorylates RanGDP to form RanGTP

21
Q

How is cargo exported from the cell nucleus?

A
  • Cargo binds to an exportin and RanGTP in the nucleus
  • Complex carried out by the nuclear pore complex
  • RanGTP and cargo are released to the cytosol
  • exportin travels back into the nucleus via the nuclear pore
22
Q

How is cargo imported into the cell nucleus?

A
  • Cargo binds directly to the importin and travels into the nucleus via the nuclear pore
  • Importin then binds to RanGTP which then allows it to be carried back out of the cell via the nuclear pore complex
23
Q

How do karyopherins allow cargo to enter and exit the nuclear pore?

A

Interact with FG repeats in the lumen of the nuclear pore

24
Q

What do RNAs exist in the cell as?

A

ribonuclear protein complexes

25
Q

How is correctly processed mRNA exported from the cell nucleus?

A

Assisted by the activity of RNA helicase Dbp5

BL2301 Cell Biology (17 decks)

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