The nucleus Flashcards
How many genes do bacteria have?
1000-6000
What roles does the nucleus undertake?
- separates transcription from translation
- it enables alternative splicing
- allows for multicellular organisms with different cell population
Why doesn’t alternative splicing occur in bacteria?
No nucleus
What are the 2 hypothesis of the origin of the nucleus?
- Invagination
- Endosymbiosis
Describe the process of invagination as an origin of the nucleus
The DNA is in the cell, with the ribosomes bound to the membrane. The membrane then invaginates and eventually forms around the DNA.
Describe the process of endosymbiosis as an origin of the nucleus
The engulfment of bacteria resulting in organelles such as mitochondria, chloroplast.
Describe where mitochondria has come from
Bacteria (bacteria that has been engulfed)
How many proteins is a histone octamer made of?
8
DNA is wrapped around histones to form what?
nucleosides
What is heterochromatin?
DNA material of a high density staining
What is euchromatin?
DNA material of a less dense staining
What is the nucleolus (think staining)?
DNA material that stains densely
What is chromosome called when not in a dividing stage?
Chromatin
What technique can be used to view specific chromosomes?
Chromosomal painting
What is the nucleolus’ function?
Ribose synthesis
What is the speckles’ function?
Pre-mRNA processing
What is the function of the Cajal bodies?
Splicing
What is the function of PML (promyelocytic leukemia protein) bodies?
Storage depot
What is Fen1-GFP?
damage repair protein
What is micro-radiation?
Laser used to introduce damage at a specific point in cell
Why is micro-radiation useful?
allows ability to observe repair factories
How does the nucleolus synthesize ribosomes?
through the production of rRNA, which is then processed and assembled into the nucleus
Does the nucleolus have a membrane?
NO
When does the nucleolus dissociate?
during mitosis
How many membranes does the nuclear envelope have?
2 - inner & outer
What is the outer membrane of the nuclear envelope’s composition?
Continuous membrane with the ER (endoplasmic reticulum) & contains ribosomes
What is the inner membrane of the nuclear envelope’s composition?
Contains proteins that anchor the chromatin
What is the function of the nuclear lamina ?
maintains the structure of the nuclear envelope on the inner membrane
How does the nuclear envelope disassemble during mitosis?
the nuclear envelope becomes detached from the NPCs (nuclear pore complexes)
What type of staining allows us to visualise the nuclear envelope?
DAPI staining
What is the nuclear envelope made up of?
Lamins
What are laminopathies?
defects in nuclear lamins that can cause conditions such as Hutchinson-Golford progeria syndrome
What roles can laminas be said to play, as a result of the defects caused by laminopathies?
- gene regulation
- structural rigidity
What is transported into the nuclear pore?
proteins
What is transported out the nuclear pore?
tRNA & mRNA
How many proteins are there that are nucleoporins?
30
What technique has allowed research into NPCs (nuclear pore complex)?
Electron microscopy
How does water & water-soluble molecules travel into the nucleus?
NPCs (nuclear pore complex)
What method is used to transfer proteins larger than 60,000 Da across the NPC (nuclear pore complex)?
Active transport
What are nuclear localisation signals (NLS) used for?
when proteins are imported into the nucleus, they use NLSs to reach their target destination
What amino acids are Nuclear Localisation Signals (NLS) rich in?
lysines & arginines
What type of proteins belong in the nuclear transport receptor family?
Nuclear Import proteins (NIPs) - importins
Nuclear Export proteins (NEPs) - exportins
