Nucleus Flashcards
Do prokaryotic cells have nucleus?
No, only eukaryotes do.
Why is the nucleus useful to have in a cell?
Allows complex gene organisation, regulation etc.
Describe the structure of the nucleus
Double membrane bound organelle
Difference between Hetero/Euchromatin?
Hetero = inactive DNA Eu = active DNA
Steps to chromatin packing
- ) DNA helix wound around histome proteins to form nucleosomes.
- ) Folding and super condensing turn DNA into a fiber (250nm wide).
- ) Tight cooling of fiber forms chromatid of chromosome.
What is a chromatid?
A newly formed replicate of a chromosome that is still joined to the original chromosome by a centromere.
What is the pro-myelocytic leukemia bodies used for?
Storage of protein complexes used for DNA repair. A repair shop.
What is the role of a cajal body?
Process snRNA and snoRNA. Make snRNPs used for RNA-splicing.
Speckles?
Storage of mature snRNPs
What is the role of the nucleolus?
Main function is to produce ribosomes. Process non-coding RNAs, SRPs.
Where are the subunits of ribosomes produced?
In the nucleolus of nuclei.
Describe the structure of the nuclear envelope.
A double lipid bilayer that is connected to the RER.
Role of nuclear pores?
Allows selective transfer of substances
How is nuclear import regulated?
Via specific signal sequences on proteins
Where would you find the nuclear lamina?
Covering the inside of the nuclear envelope
