The nucleus

when are chromosomes visible

They are visible during mitosis

what is the basic unit of chromatin

nucleosomes

what are the two parts of the nuclear envelope

• inner nuclear membrane

• outer nuclear membrane

as dna condenses what are the names of it at the first 4 stages

• DNA

• nucleosomes

• chromatin fibers

• chromosomes

what does chromatin consist of

• DNA

• histone and non histone proteins

how much of chromatin is DNA by mass

1/3rd

what is one way you’d test if chromatin were all DNA or if they had some proteins

I would distribute nucleases and see if anything would be left over

name all the parts of the histone protein

• H1

• h2A

• h2B

• H3

• H4

recognition on what part of the histone is very important

The histone tail

how can nucleosomes be dynamic

they Dna be moved by ATP dependent chromatin remodeling complexs

is the H1 histone part of the core histone molecule

no it is in the linker regions

how does the h1 histone aid in the compaction of DNA

it stabilizes interactions and permits them between the nuclear core components

define euchromatin

active gene expression, DNA replication and repair

define heterochromatin

gene silencing, genome stability and chromosomal integrity

what are the two types of heterochromatin

• facultative

• constitutive

how is facultative chromatin different from constitutive chromatin

facultative chromatin has the ability to uncondense and become active while constitutive cannot

what are some modifications that can be made to the histone tail

• acetylation

• methylation

• phosphorylation

what effects can these tail modifications have on the dna

• can form heterochromatin and silence gene

• can increase gene expression

what is another way histones can be modified

variants of the histone proteins may be inserted into the sequence

what recognizes histone modifications

reader complexes

what blocks the spread of heterochromatin

barrier proteins

what are lampbrush chromosomes

they are sections of chromatins that are uncondensed

how would we test to confirm that gene activation leads to decondesation of chromatin

place a GFP fluorescent molecule on a repressor and activator and track the size of the fluorescence

what are two ways to track nuclear territories or chromosome proximity

• chromosome painting

• chromosome conformation capture

How does chromosome conformation capture work

basically fusing together close chromatin and testing whether they are of two different genes/chromosomes

how does the body[ prevent dna from becoming too wound

proteins like the SMC protein

what is the purpose of the SMC protein

it is a dna position holder that in bacteria prevent dna from super coiling

how are euchromatin and heterochromatin spatially seperated in the nuculeus

the euchromatin is in the center while the heterochromatin exists on the edges

how does the position of euchromatin vs heterochromatin manifest in active gene transcription

if a gene is active it can be seen moving toward the middle of the nucleus

what is the nuclear pore complex

present in all eukaryotes and allows proteins to travel to and from the nucleus

what is the nuclear lamina

a meshwork of lamins that are anchored into the inner nuclear membrane and hosts the nuclear pore complexes

describe the structure of the nuclear pore complex’s

• cytoplasmic filaments

• outer ring

• FGC

• transmembrane ring

• inner ring

• nuclear basket

in nuclear pore complex’s what proteins resemble vesicle coats

Nups

why is the simmilarties of vesicle coats to Nups important

it is important because it explains how NPC were formed in evolution

what directs proteins towards the nucleus

Nuclear localization signals

do all proteins entering the nucleus require a localization signal

no if they are small enough the can enter though diffusion

if the molecule is too large, but has a nuclear localization signal what happens

they bind to nuclear import receptors

How do nuclear import receptors transport the cargo into the nucleus

the import receptors have fg binding sites that allow them to pass through nuclear pore complexes

does the binding of NLS sequences to import receptors have to be direct

no, it can be indirect through adaptor proteins

How is it ensured that molecules only enter the nucleus and don’t leave

Ran-GTP causes a conformational change in the import proteins that prevents it from leaving the nucleus bound to cargo

where is the concentration of ran GTP highest

nucleus

where is the concentration of ran GDP the highest

the cytoplasm

the enzymes gef and gap are critical in ensuring the movement of proteins are regulated into the nucleus where are they present

• Gef is present in the nucleus

• GAP is present in the cytoplasm

how do nuclear export receptors work

they work the opposite of import receptors

what are the ways protein import and export of the nucleus may be regulated

• protein modification

• protein conformation

• protein interaction

• cytosolic retention