Exam 1 study guide questions Pt. 3

why are the R groups of histones facing each other

prevent unwated chemical bonds between the histone octamer and the DNA, protects the DNA, allows DNA to interact with other things, allow hisotne to bind to nay DNA sequence, allows nuclsome to “roll”

what part of the amino acid chain does the DNA interact with

positively charged amino acids

at what point in the cell cycle do chromosomes condense, How does this happen

In G2 - with condensin

what is the difference between trans and cis movement of histones

cis is direct result of modification, trans - an outside chromatic remodeling complex is attached and does modifying

what do HAT protiens do

turn a gene on by acetylating the histone tail, bromodomain moves it apart

what do HDAC proteins do

deacetylate the histone tail - chromodomain binds moves closer and turns it off

what are the effects of ubiquination

signals destruction in most proteins, proteasomes chew it up, used to signal DNA replicaiton or repair

what is the difference between trans and cis movement of histones

cis alters without other molecules, trans requires other proteins

in terms of chromatin remodeling complexes what do chromodomains and bromodomains do

bromodomain- acetylate (on) chromodomain- methylate (off)

at what point in the cell cyle are histones made

G1 - so when DNA is copied in S phase the histones are available to wind the DNA and G2 for H1 - so chromatin can be compacted in prophase

how are histones ditrubuted durring the DNA replicaiton process?

H2A and H2B get thrown off nucleosome leaving behind H3 and H4

what happens to H2A and H2B durring replicaion

the leave histone and randomly go back

what must be done to the new histiones that are added to the DNA strands

they must have the same modifications as the old ones

How are epigenetics states propagated throughout the genome

Histones and tail modifications can be preserved during replication

what is meant by the histone code

different combinations of histone tail modifications will send specific signals to direct gene expression, don’t know specifics but know that they exist and are important

what is mitochondrial DNA

mitochondria have their own DNA separate from the nucleus of the cell

what is a twist

ribbon tiwist of DNA, - the shape the helix makes itself

what is a writhe

roller coaster twist of DNA - looks like loops, when twists fold on themselves

what purpose do DNA scaffolding protiens serve

combine other molecules into a complex to complete a task

how do DNA scaffolding proteins interact with DNA

constrain coiled DNA to form chromosomes

what is underwound vs. overwould DNA

DNA enters the polymerase underwound (negative, righthanded) supercoil and leave as overwound (positive, left-handed) supercoiled

what is the linking number

twist + writhe

what are SMC proteins

structural Maintenace of chromosomes

what does cohesin do

hold sister chromatids together

what does condensin do

condense DNA → chromosomes

what does seperase do

removes cohesion from chromosomes

when is cohesin made

G1

when is condesin made

G2

when is seperase made

G2

when is cohesin used

S phase

when is condensin used

prohase

when is separase used

metaphase