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38 Cards in this Set

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What is the nuclear lamina?
What laminates the inside of the nuclear membrane - on the inner side - bound to it.
What is the nuclear lamina's function?
To maintain the sherical shape of the nucleus when the nuclear envelope breaks down during interphase.
What happens to the nuclear lamina after interphase?
It breaks down due to hyperphosphorylation of its proteins.
What is the nuclear lamina made of?
3 Intermediate filament-like proteins
What 3 things are related to / associated with the nuclear lamina?
1. Marginal heterochromatin (in)
2. Inner nuclear membrane (ext)
3. Nuclear pore complex
What are the IF-like proteins that make up the nuclear lamina?
Lamins A/B/C
What is the function of each lamin protein?
Lamins A/C interact w/ marginal heterochromatin

Lamin B binds inner nuclear membrane via LBR
What is LBR?
Lamin B-receptor - on the inner nuclear membrane, it is an integral membrane protein.
Why is Lamin B so important?
Because it stays attached to the nuclear lamina during mitosis so that when the nuclear envelope reforms it will have a skeleton to do it onto.
What happens if no lamin-B?
No nuclear envelope = no nucleus
What causes the nuclear lamina to break down at interphase?
Hyperphosphorylation of Lamins A and C
When during mitosis does the nuclear lamina break down?
During prophase
When does the nuclear lamina reform?
During telophase
What happens when lamins are mutated?
The nuclear lamina is disorganized and DNA synthesis is inhibited
How are the lamins encoded?
Lamins A/C = one gene, LMNA
Lamin B = its own gene
What are 3 results of LMNA mutation?
1. Muscular dystrophy
2. Cardiomyopathy
3. Premature aging
What is a lamin mutation called?
Laminopathy
What makes up by far the most of the nuclear matrix?
Internal nuclear matrix - 99%
What is the main function of the internal nuclear matrix?
Gives NONRANDOM order to chromatin
What does the nonrandom order conferred by nuclear internal matrix do?
Ensures normal duplication and transcription of genes.
What happens if the internal nuclear matrix is abnormal?
Cancer or cellular necrosis
3 Things we know about the internal Nuclear Matrix:
1. Chromosomes are positioned nonrandomly
2. Matrix proteins are tissue specific
3. Nuclear matrix functions in DNA replication/transcription.
Stages in the cell cycle:
G1
S
G2
M
What happens in G1
Chromatids de-condense; RNA and protein synthesis begin
What happens in S
DNA and histones synthesized
What happens in G2
Preparation for mitosis
Centrosome is duplicated
What happens in M
Cells round up, nuclear envelope disintegrates, chromotin condenses to form chromatids which line up and segregate to daughter cells.
What is Interphase?
G1-S-G2
What is Generation Time?
The time for one revolution through all phases (G1-G1)
Which phase is most variable?
G1
What is the function of Mitosis?
To restore the 2N condition to the 4N product of Sphase
What are the steps in mitosis?
PPMATC
Prophase, Prometaphase, Metaphase, Anaphase, Telophase, Cytokinesis
Prophase
-hyperphosphorylation
-chromatin-tid condensation
-Centrosomes form spindle poles
Prometaphase
formation of mitotic spindles
Microtubules/kinetochores appear
(astral/polar/kinetochore)
Nuclear envelope disintegrates
Metaphase
chromosomes align at equator
Anaphase
Chromosomes move to opposite poles
Telophase
formation of daughter nuclei
Cytokinesis
Completely separate cells