Nucleus Worksheet Flashcards
(32 cards)
How is the genetic material organized into functional regions?
What processes take place in each region?
nuclear speckles - mRNA splicing
cajal bodies - RNP
nucleolus - rRNA
What are nuclear speckles?
storage sites of splicing components, which are then recruited to actively transcribed genes where pre-mRNA processing occurs
What are Cajal bodies?
site of snRNP assembly
Compare euchromatin and heterochromatin.
eu - actively transcribed
hetero - varies according to cell type, non-transcribed, frequently located close to nuclear membrane
What is the function of the nucleolus?
rRNA transcription and processing, ribosome assembly
What are the parts of the nucleolus?
What process takes place in each region?
fibrillar center - location of rRNA genes
dense fibrillar component - active in transcription of rRNA
granular component - site of ribosome assembly
How are ribosomal RNAs processed?
45S pre-rRNA cleaved into 18S, 28S, and 5.8S pieces
Where are ribosomal proteins synthesized?
cytoplasm
Where are ribosomal proteins combined with the rRNAs?
nucleolus
What is the structure of the nuclear envelope?
outer nuc. membrane - cont. w/ ER
perinuc. space - lumen - cont. w/ ER
inner nuc. membrane - binds nuc. lamina and chromatin
What are nuclear pores?
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
What is the nuclear lamina?
meshwork underlying inner nuclear membrane, provides shape and stability to nuc. envelope
What are the components of the nuclear lamina?
lamins (IF’s) and associated proteins (integral membrane proteins) - attach lamina to membrane
What are the clinical implications of mutations in the components of the nuclear lamina?
can cause diseases like Hutchinson-Gilford progeria
What are signal sequences?
read the phrase
Compare nuclear import signals to nuclear export signals.
import - basic aa, Lys. and Arg.
export - rich in leucine
What types of molecules are transported from the cytoplasm into the nucleus?
histones, replication and transcription machinery, ribosomal proteins, TF’s
What types of molecules are transported from the nucleus to the cytoplasm?
proteins and RNAs
What carrier molecules are involved in nuclear import? Export?
importins and adaptors
exportins
How do protein modifications regulate the transport of cargo between the nucleus and the cytoplasm?
modifications act like address labels, tells the protein that it needs to go in or out
What is the function of small GTPases?
molecular switches
What is Ran?
controls directionality of movement through nuclear pore
What are GTPase activating proteins? (GAPs)
stimulates intrinsic GTPase activity
Where is Ran-GAP localized in the cell?
cytoplasm
