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EoM: Exam 2 > Nucleus Worksheet > Flashcards

Nucleus Worksheet Flashcards

1
Q

How is the genetic material organized into functional regions?
What processes take place in each region?

A

nuclear speckles - mRNA splicing
cajal bodies - RNP
nucleolus - rRNA

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2
Q

What are nuclear speckles?

A

storage sites of splicing components, which are then recruited to actively transcribed genes where pre-mRNA processing occurs

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3
Q

What are Cajal bodies?

A

site of snRNP assembly

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4
Q

Compare euchromatin and heterochromatin.

A

eu - actively transcribed

hetero - varies according to cell type, non-transcribed, frequently located close to nuclear membrane

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5
Q

What is the function of the nucleolus?

A

rRNA transcription and processing, ribosome assembly

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6
Q

What are the parts of the nucleolus?

What process takes place in each region?

A

fibrillar center - location of rRNA genes
dense fibrillar component - active in transcription of rRNA
granular component - site of ribosome assembly

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7
Q

How are ribosomal RNAs processed?

A

45S pre-rRNA cleaved into 18S, 28S, and 5.8S pieces

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8
Q

Where are ribosomal proteins synthesized?

A

cytoplasm

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9
Q

Where are ribosomal proteins combined with the rRNAs?

A

nucleolus

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10
Q

What is the structure of the nuclear envelope?

A

outer nuc. membrane - cont. w/ ER
perinuc. space - lumen - cont. w/ ER
inner nuc. membrane - binds nuc. lamina and chromatin

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11
Q

What are nuclear pores?

A

nucleoporins form a ring, anchored to membrane and nuclear lamina, fibrils on cytoplasmic side bind cargo and direct transport through pore, fibrils on nuclear side end in basket-like structure

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12
Q

What is the nuclear lamina?

A

meshwork underlying inner nuclear membrane, provides shape and stability to nuc. envelope

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13
Q

What are the components of the nuclear lamina?

A

lamins (IF’s) and associated proteins (integral membrane proteins) - attach lamina to membrane

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14
Q

What are the clinical implications of mutations in the components of the nuclear lamina?

A

can cause diseases like Hutchinson-Gilford progeria

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15
Q

What are signal sequences?

A

read the phrase

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16
Q

Compare nuclear import signals to nuclear export signals.

A

import - basic aa, Lys. and Arg.

export - rich in leucine

17
Q

What types of molecules are transported from the cytoplasm into the nucleus?

A

histones, replication and transcription machinery, ribosomal proteins, TF’s

18
Q

What types of molecules are transported from the nucleus to the cytoplasm?

A

proteins and RNAs

19
Q

What carrier molecules are involved in nuclear import? Export?

A

importins and adaptors

exportins

20
Q

How do protein modifications regulate the transport of cargo between the nucleus and the cytoplasm?

A

modifications act like address labels, tells the protein that it needs to go in or out

21
Q

What is the function of small GTPases?

A

molecular switches

22
Q

What is Ran?

A

controls directionality of movement through nuclear pore

23
Q

What are GTPase activating proteins? (GAPs)

A

stimulates intrinsic GTPase activity

24
Q

Where is Ran-GAP localized in the cell?

A

cytoplasm

25
Q

What are guanine nucleotide exchange factors? (GEFs)

A

molecules that promote exchange of GDP for GTP

26
Q

Where is Ran-GEF localized in the cell?

A

nucleus

27
Q

What is the Ran cycle?

A

cytoplasm: RanGAP stim. RanGTP –> RanGDP —-> nucleus

nucleus: RanGEF stim. RanGDP –> RanGTP —-> cytoplasm

28
Q

What is the mechanism of Ran dependent transport for IMport?

A

(c) NLS recognized by importin, importin/cargo goes through pore, (n) Ran/GTP binds to importin, complex disrupted, cargo released into nucleus, importin-Ran/GTP exported out through pore, (c) RanGAP stim. RanGTP –> RanGDP, importin released

29
Q

What is the mechanism of Ran dependent transport for EXport?

A

(n) cargo, NES, exportins, and RanGTP form complex, go through pore, (c) RanGAP stim. RanGTP –> RanGDP, cargo and exportin released

30
Q

What is the mechanism of Ran indepedent transport?

A

(n) molecule bound by exporter complex, goes through pore, (c) helicase releases molecule

31
Q

What type of molecules are transported by Ran independent transport?

A

mRNA

32
Q

What is the structural organization of the nucleus?

A

heterochromatin, euchromatin, and chromosomes

EoM: Exam 2 (2 decks)

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