Genetic mechs Flashcards
(148 cards)
1
Q
What did Levene correctly and incorrectly determine in DNA structure
DNA rep history
A
Corr - DNA made from nucltid, structure of nucleotide
Incorr - Tetranucleotide hypothesis (bases form circle, equal ratio of all bases)
2
Q
What did Chargaff figure out and how did it refute Tetranucleotide hypothesis (levene)
DNA rep history
A
A pairs with T
G pairs with C
Ratio of A and T does not affect G, C
Ratios can be diff
3
Q
What was error in pauling triple helix model
DNA rep history
A
not triple helix
phosphates were located in core of helix
negative O would repel in reality
4
Q
what was technique used by franklin and wilkins to determine DNA structure
DNA rep history
A
X ray crystallography - DNA sample crystallized, shoot xrays, measure defraction to find 3d structure
5
Q
signifigance of watson and cricks base pairing
DNA rep history
A
finalized structure
inspired by alpha helix protein shape
won prize
found location and angle
6
Q
conservative vs semi conservative vs dispersive model
DNA rep
A
conservative - whole parent DNA preserved, complete new copy made
semi cons - correct - half parent, half new in each
dispersive - bits of parent, bits of new in chunks
7
Q
What were the steps in Meselson and Stahls exp
DNA rep
A
- grew ecoli in heavy nitrogen (N15)
- transfer ecoli to lighter N14, 1 reproduction, centrifuge
- see 1 band (cant be conservative )
- 1 more replication in N14, centrifiuged
- see 2 bands (cant be dispersive)
Must be semi conservative
8
Q
What would each DNA rep model look like after the first centrifuge
DNA rep
A
conservative - 2 band (complete parent , complete new)
semi cons- 1 (2 half/half)
dispersive - 1 (mix of both averages out)
9
Q
What would each DNA rep model look like after the second centrifuge
DNA rep
A
cons - 2 (3 new on top, 1 parent bottom)
semi cons - 2 (2 half/half, 2 fully new )
disruptive - 1 (average density)
10
Q
difference between prokaryote and euk DNA rep init
DNA rep
A
prok - rep begins at 1 certain point, 1 bubble expands
Euk - rep begins thousands of places at once on dna, bubbles form
11
Q
What is an Ori
DNA rep
A
Origin of replication
Special sites on DNA where replication begins
Contains a specific sequence recognized by the replication machinery (enzymes)
Often high in A-T base pairs
12
Q
Steps and proteins in DNA rep init
DNA rep
A
initiator protein unwinds the DNA
helicase seperates strands
Single-strand binding proteins (SSBPs) - keeps them apart
Topoisomerase
primase makes primer
13
Q
Why is priming needed
DNA rep
A
New nucleotides can only be added to the 3 end
14
Q
DNAP I vs DNAP III
DNA rep
A
both found in prok
DNAP III catalyzes elongation, adds nucleotide to existing 3’ end, ntide is hydrolyzed
DNAP I - replaces the RNA primer with DNA
15
Q
what is the problem wtih rep fork as it relates to anti parallel nature of DNA
DNA rep
A
due to anti parallel nature of DNA one of the new DNA strand will have 3’ end at fork and the other will have 5’ end at fork
New nucleotides can only be added to 3’ end
but both new DNA strands must be built
16
Q
diff in steps and enz for leading and lagging strand
DNA rep
A
leading - primase makes 1 primer,DNAP III builds off it, 1 DNAP used at ori
lagging - primase makes primer, DNAP III builds off it, DNAP I replaces primer, DNA ligase, happens multiple times
17
Q
what is okazaki fragment
DNA rep
A
fragments of new DNA on lagging strand
18
Q
What is leading and lagging strand
A
leading - synthesized continuously, polymerized in direction of fork
Lagging - synthed in short okazaki fragments, polymerized opposite direction of fork
19
Q
what is telomere
DNA rep
A
bunch of useless DNA at end of chromosome
starts with 15000 at cenception
death with 5000
20
Q
What does topoisomerase do
DNA rep
A
breaks DNA bonds and reforms them
helps to unwind DNA and lower tension
on either side of bubble
21
Q
What does helicase do
DNA rep
A
disrpts H bonds in DNA and seperates DNA to make the fork
in base of fork
22
Q
What do single stranded binding proteins do (SSBPs)
DNA rep
A
binds to unwound DNA strands keeps it apart
23
Q
What is an RNA primer
DNA rep
A
made by primase so that the DNA has something to attach to
is eventually taken out
24
Q
WHat is 3’ and 5’ end
DNA rep
A
Has to to with which carbon is exposed.
Nucleotides can only be added to the 3’ end.
25
What does DNAP I do
## Footnote
DNA rep
replaces the RNA primers with DNA, takes place after the DNAPIII
26
if DNA nucleotides can only be added to a 3' end, how does DNAP I add new DNA?
it adds it to the 3' end of the strand before it
27
What does DNAPIII do
## Footnote
DNA rep
Adds to the 3' end of an existing strand
28
What does DNA ligase do
## Footnote
DNA rep
Binds together the okazaki fragments after they are completely DNA
also used to bind the 2 DNA at ori
uses phosphodiester bonds
29
Eukaryote vs Prok rep termination
## Footnote
DNA rep
euk - when bubble reach another bubble, when it reaches end of DNA
prok - when it circels around to beginning of bubble
30
what is the replication problem at the end of linear DNA
## Footnote
DNA rep
There was a primer used to start to make the 5' end that was removed meaning that the ends do not line up, some of the original DNA was not copied. happens with the lagging strand
31
what is purpose of telomeres and structure
## Footnote
DNA rep
found at end of euk chromosomes
noncoding
made from repeats of short genetic sequence
protects DNA from being eroded, getting unound
32
what is senescence
## Footnote
DNA rep
when the cell stops growing or dividing, recognizes that DNA is damaged, will not divide for protection
33
what is apoptosis
## Footnote
DNA rep
programmed self descructtion
34
what is the cellular concequence of shortened telomeres
## Footnote
DNA rep
senescence or aptosis
35
what is telomerase and what does it do
## Footnote
DNA rep
enzyme that adds telomeres to chromosomes
is a ribonucleoprotein
does reverse transcriptase
36
what is a ribonucleoprotein
## Footnote
DNA rep
protein that contains RNA in it and protein
ex human telomerase contain RNA (AAUCC)
37
what is reverse transcriptase
## Footnote
DNA rep
When RNA is used to make DNA instead of the other way around
ex. Telomerase uses its internal RNA to make the DNA for the 3' of chromosmes (makes the longer part longer )
38
How do telomeres relate to aging
## Footnote
DNA rep
they get shorter as you age
15000 bases at conception
10 000 at birth
5000 at death
39
How the telomere is completed using telomerase
## Footnote
DNA rep
1. binds to 3' (parent strand)
2. extends the parent using its RNA template
3. the other complimetnary strand gets primer with primase
4. DNAP alpha is used to elongate
5. DNA ligase connects the newcomplementary strand with the rest of the complimentary strand
6. still end up with the parent strand being longer than the complimentary strand but technically nothing is lost. (eveything needed is copied)
40
What cells contain telomerase acivity
## Footnote
DNA rep
germ cells and cancer cells
41
Do eukaryotes use DNAP I and III
## Footnote
DNA rep
No
eukaryotes use ones named with greek letters (15)
prok have 5 DNAP (roman numerals )
DNAP alpha is like DNAP III but for euk
DNAP also seems to make the primer?
DNAP delta is like DNAP I?
42
why does DNAP alpha make telomeres instead of DNAP III
## Footnote
DNA rep
Telomeres only exist in eukaryotes
the issue only needs to be solved in eukaryotes
DNAP III is used in prokaryotes only and does not need to be able to make telomeres
DNAP alpha is used in eukaryotes only
43
What is a gene
## Footnote
Transcript
stretch of DNA that is transcribed into RNA
aka transcription unit
44
What is a promoter and why does it have rich AT regions
## Footnote
Transcript
Where the RNAP first binds
upstream of gene
holds TATA box
holds transcription start point
Rich in AT because they are easier to break apart and start transcription
45
transcrition initiation in euk vs prok
## Footnote
Transcript
prok - RNAP recognizes promoter, binds, unwinds DNA, starts
euk - pre - initiation complex made (protein factors + anactive RNAP II), RNAP gets phosphorylated at C terminal domain, starts
46
What is coding strand
## Footnote
Transcript
strand of DNA whos base sequence is identical to the RNA
not the template
47
What is the sense strand
## Footnote
Transcript
same as the coding strand
it is the one what looks like the RNA
48
what is the antisense strand
## Footnote
Transcript
the template for the RNA
complimentary to the sense strand
does not mean anything by itself
49
What is the RNA Transcript
## Footnote
Transcript
WHat initially comes out of transcription before the post processing
primary Transcript
newly synthed RNA
50
Where does Transcript take place
| in cell, euk vs prok
## Footnote
Transcript
euk - nucleus
prok - cytoplasm
51
51
Where does translation take place
| prok vs euk
## Footnote
translation
both take place in cytoplasm
euk - leaves nucleus after transcript
prok - does not have nucleus
52
How do you know the 3' end 5' of DNA based off RNA
## Footnote
Transcript
RNA must be made be made in direction of 3' end
sense strand is in same direction as RNA
antisense strand / templete - is opp direct of RNA
53
Transcription termination for euk
| 4
## Footnote
Transcript
1. dephosphorylation of C terminal domain on RNAP II (slows it down)
2. AAUAAA gets Transcribed, stalls RNAP II, but continues
3. GU rich region, gets transcribed, signals endonuclease to cut
4. cut happens after AAUAAA, before GU region on RNA
54
transcription termination for prok
## Footnote
Transcript
1. 2 GC rich regions that are complimentary
2. when transcribed form hairpint
3. dA region on DNA make U region on RNA, weak bonds
4. RNAP stops and is released
55
How are Transcription termination different euk vs prok
## Footnote
Transcript
prok - uses hairpin method
Euk - uses endonuclease to cut RNA off from RNAP
56
What are the types of RNAPs used euk vs prok
## Footnote
Transcript
prok - only hase 1 types of RNAP
Euk has 3 types, mainl RNAP II used
57
What is mRNA
## Footnote
Transcript
messenger RNA
final transcript, what gets translated
leaves neucleus
58
What are the 3 types of RNA processing do both euk and prok have it
## Footnote
Transcript
capping
polydenylation
splicing
only euk does this
59
What is capping (what, where, why, when)
## Footnote
Transcript
at 5' end of new RNA
addition of modified guanine
protection from degredation, helps ribosomes bind
during transription
60
What is polyadenylation (what, where, why, when)
## Footnote
Transcript
3' end
addition of many adenine (poly A tail)
protection, facilitation of mRNA export
after Transcription
61
What is splicing (what, where, why, when)
## Footnote
Transcript
introns
intron is taken out
for alternative splicing, exon shuffling
during and after transcription
62
components of splicing
## Footnote
Transcript
Splice site (on RNA)- on ends of intron, where snRNPs binds
Spliceosome - contains snRNPs+ other proteins
- snRNP - contains snRNA and protein
63
What are snRNPs and what do they do
## Footnote
Transcript
Part of splicing, turing RNA into mRNA
small nuclear ribonucleoprotein
is a rybozyme - has RNA is catalyzer, not protein
binds to splice site to get rid of a specific intron
64
What are the mechinisms of splicing
## Footnote
Transcript
2 snRNP binds to intron ends (snRNA is complimentary to the splice site)
More proteins come in to make spliceosome
introns are cut out
exons are rejoined
65
How can splicing be recognized in a photo
## Footnote
Transcript
loops formed in the RNA
66
What are introns and their function
## Footnote
Transcript
interveneing
noncoding sequences in between exons
regulate gene expression through alternative splicing
67
what function of introns have direct relevence to Transcription
## Footnote
Transcript
introns can are used in alternative splicing
allows one gene to make many diff polypeptides by considering different things as introns
68
What are the 4 steps in translation initiation
## Footnote
translate
1. small unit of ribosome finds and binds to mRNA
2. small unit ribosome finds start codon (AUG) along mRNA
3. initiator tRNA binds
4. large unit of ribosome binds, takes GTP, tRNA in P site
69
prok vs euk translation initiation (compare 4 steps )
## Footnote
translate
1. prok - has shine-Dalgarno seq, helps small ribo find start
euk -small ribo binds
2. prok - has initiation factors
euk - has kozak sequence before start to help locate
3. prok - starts with fmet
euk - starts with met
4. both - large ribo binds
70
What is shine dalgarno sequence
## Footnote
translate
prok version of 5' cap
helps ribosome find 5' end of prok mRNA
71
what are 2 subunits and 4 binding sites in ribosome
## Footnote
translate
large top subunit, small bottom subunit
has A site, P site, E site, mRNA binding site
72
What is translation initiation complex
## Footnote
translate
complete ribosome+ initiator tRNA at P site+ mRNA at AUG
73
What is codon and anticodon
## Footnote
translate
codon - 3 consecutive nucleotides on RNA, codes 1 amino acid
anticod - complimentary sequence to codon on tRNA
74
What are the parts of tRNA molecule and what does it look like
## Footnote
translate
is clover shaped in 2d
L shaped in 3d
3' end holds amino acid
Anticodon is on bottom
75
describe steps of translation elongation
## Footnote
translate
1. codon rec - tRNA with right anticodon enter A site, H bonds form btwn mRNA and antocod, uses GTP eng
2. pep bond formation - ribo catalyzes reaction in amino acid in P and A, polypep on tRNA in P site moves to tRNA in A site, polypep is 1 longer
3. translocation - tRNA in P moves to E and leaves, tRNA in A moves to P, takes GTP eng, next tRNA can enter
76
What is direction of reading in translation
## Footnote
translate
ribosome reads from 5' end to 3' end of mRNA
77
Where is the C terminus and N terminus of growing peptide chain
## Footnote
translate
C terminus is where new amino acids are added
N terminus is where the start amino acid it
78
How is translation terminated
## Footnote
translate
at stop codon no tRNA
release factor binds, adds water instead of amino acid
polypep gets hydrollyzed
ribosome disassebles
79
How to know 5' and 3' end in polyribosome on RNA
| also what is polyribosome
## Footnote
translate
polyribo - when 1 mRNA has many ribo translating at once
translation starts at 5' end
translating towards DNA
closer to DNA = been translating longer
80
Location of ribosome and the type of protein it produces
## Footnote
translate
free ribo (in cytosol) - makes cytoplasmic proteins (organelles)
bound ribo (right outside right endo plasmic reticulum) - makes secretory proteins (lysosomes, membrane proteins)
81
Cytosol vs cytoplasm
## Footnote
translate
cytosol - fluid in the cell, organelles are within
cytoplasm - inside of cell, iincludes organelles
both exclude nucleus
82
what are chaperone proteins for
## Footnote
translate
allows proteins to fold by making proper microenv
used by cytoplasmic proteins
makes hydrophillic env
unfolded protein goes in
chaperone gets capped, changes
folded protein out
83
What is the process of trafficking secretory proteins
| 7
## Footnote
translate
1. signal seq made at N term
2. SRP binds to sig seq, stops translation
3. SRP binds to SRP receptor on ER, ribo is docked to outside of ER
4. sig seq goes through translocon, into ER lumen, SRP leaves, translation cont
5. signal peptidase cuts of sig seq
6. translation continues
7. translation completes, polypep releases into ER lumen
84
what is signal sequence
## Footnote
translate
all ribos start off free
If N terminus has signal sequence the ribo will stop and go to ER to continue
first step of secretory proteins
5-30 hydrophobic amino acids
85
what is stop transfer sequence
## Footnote
translate
part of the peptide that anchors it to the ER membrane, stops it from being fully released into ER lumen
C terminus out, N terminus in ER
86
what si SRP
## Footnote
translate
Signal recognition particle
recognizes signal sequence and takes the ribosome and everything to ER to continue translation
87
waht is translocon
## Footnote
translate
like a channel protein
places where the polypep goes through to get into ER
88
waht is signal peptidase
## Footnote
translate
cuts off the signal sequnce once its in the ER lumen
89
What is SRP receptor
## Footnote
translate
where the signal recognition particle binds to the ER
found on cytosolic side of ER
90
cell membrane proteins vs secreted proteins
| compare making process
## Footnote
translate
Cell membrane proteins have stop transfer sequence, it keeps them in the ER membrane and eventually sends them to cell memb
proteins that are secreted out do not have transfer seq
91
organelles in endomembrane system and their roles in protein trafficking
| 4
## Footnote
translate
Endoplasmic reticulum - folds proteins
Golgi complex - for post translational mods
lysosomes - some proteins become them
vesiclesé - transports the polypep to membrane of cell
## Footnote
page 51 of translate slides
92
What are the steps in secretory system to ER
## Footnote
translate
1. sig seq translated, process slows
2. Signal rec protein, comes brings it to SRP receptor
3. protein sent through translocon, sig seq stays in translocon
4. translation continues into ER, forms loop ish thing
5. signal pepdase cuts off sig seq
6. polypep released
93
what are all the post translational mods
| 4 (ACPF)
## Footnote
translate
addition - phosphate, sugar, lipid groups added
cleavage - some amino acids removed ex. met
polymerization - 2 or more polypep form whole protein as subunits (hemoglobin)
folding - ex insulin
94
What are all the ribonucleoproteins studed in this unit
## Footnote
translate
Telomerase, snRNPs, (spliceosome)
ribosomes
95
What are the 3 chars of genetic code
## Footnote
mute
universal - all living things use same bases
redundant - diff codons code for same amino acid
non - ambiguous - each codon makes specific amino acid
96
What is wobble hypthesis and why importance
## Footnote
mute
wobble position - third position of codon
base pairing rules are flexible there
promotes redundancy
97
what is inosine and importance
## Footnote
mute
found in wobble position of tRNA
bonds with C, U, and A
allows multiple codons to make same amino acid
promotes redundancy
98
spontaneous vs induced mutations
## Footnote
mute
spont - errors from replication, from enzymes
induced - from exposure to metagenic factors
99
examples of physical mutegen and how
## Footnote
mute
UV light
makes pyrimandine dimers - when they bond next to each other instead of across the ladder
can be fixed, by the body usually
100
# ```
Perymadine dimers and what is xeroderma pigmentosum
## Footnote
mute
xeroderma - dry skin
pigmentosum - change in pigmentation
unable to repair damages caused by UV light (problem in NER mech)
leads to early skin cancer, must avoid light
101
Chemical mutagen example and how it can be used benifially
## Footnote
mute
ethium bromide
intercalating agent - gets caught in the rungs of DNA ladder
mutagen may cause DNAP to stutter and make extra base pair in rep
can be used to for staining and visualizing DNA, it glows
102
Types of DNA muataions
| 4
## Footnote
mute
1. chromosomal mutations (in meiosis)
2. missing base pair
2. fused base pair (ex. perimydine dimers)
3. mismatch (caused by point mutation), most common type
103
What is point mutation and its types (2 + subtypes)
## Footnote
mute
one nucleotide or base pair is altered
1. substitution
* transition
* transversion
2.frameshift
* insertion
* deletion
104
transition vs transversion mutation also what type is it
## Footnote
mute
DNA mutation
point mutation
substitution
transition - purine to purine, perimydine to perimydine
transversion - purin to perimydine, vice versa
105
when do DNA mutations occur
## Footnote
mute
in DNA replication
during S phase
Chromosomeal mutations can happen in mitosis
106
insertions vs deletions + special case
| what type of point mutation is it
DNA mutation
point mutation
frameshift
insertions - extra base is added
deletions - base is deleted
if multiple of 3 ins/del - no frameshift
107
Mutation classifications for polypeptide
| 3
## Footnote
mute
missense
nonsense
silent
108
what is missense mutation (def, where found, effect )
## Footnote
mute
type of polypeptide mutation
when RNA codes for diff amino acid
funciton may or may not change
ex. sickle cell anemia
109
what is a nonsense muation (def, found where, effect)
## Footnote
mute
codes for premature stop codon
type of polypeptide mutation classification
can be lethal in embryonic stage
110
what is a silent mutation (def, found where, effect)
## Footnote
mute
when mutation codes for same amino acid
type of polypep mutation
no change
111
compare diff DNA mutation effec ton polypep
## Footnote
mute
transition, transloc, - missense, nonsense, can be silent
insert or delete - extensive missense, nonsense, never silent
no frameshift, ins/del: missense, nonsense , never silent
112
# 1.
2 ways to repair DNA from mutation
## Footnote
mute
endocuclease- repairs DNA outside of replication
exonuclease - proof read as DNA is rep
113
exo vs endo nucleas repair
## Footnote
mute
exo - instant, DNAP I, II both use it, hydrolyzes phsphodiester bond and adds new nucleotide
endo - repairs after rep, mech of repair called nucleotide excision repair (NER)
114
Steps in NER and enzymes used
## Footnote
mute
1 . endonuclease - sees issue, takes off only one side
2. polymerase - fills gap with right nucleotides
3. ligase - seals it, connects new with existing nulecotides on same strand
115
why is antibiotic resistant pos even though its not good for humans
## Footnote
mute
its relative
its good for the thing that got the mutation, bacteria
116
if mRNA has 27 codons, how many amino acids in final polypep?
## Footnote
mute
26
the met (start codon) is taken out?
117
pos vs neg gene regulation
| + ex
## Footnote
expression
pos - active form of regulatory protein increases transcription of operon
ex. lac operon
neg - operons are switched off when reg protein is active (repressors )
ex trp operon - uses corepressor
lac operon - repressor starts active
118
what is operon
## Footnote
expression
a groupd of genes that share a single promoter
code for things with related functions
119
What are components of operon
## Footnote
expression
promoter - whre RNAP binds for transcription
structural genes - things to be transcribed with RNAP
2 regulatory seq - before the gene includes enhancer, operator, promoter
| order is enhancer, promoter, operator, gene, another regulatory seq
120
monocistronic vs polycistronic
## Footnote
expression
mono - in euks, promoter controls 1 gene
poly - in prok , genes with related funcitons tgt, one promoter for many genes
121
What is a constitutive gene
## Footnote
expression
regulatory genes/housekeeping genes
always transcribing
upstream of operon
unregulated
122
What is a repressible gene
## Footnote
expression
Usually on
can be turned off
corepressor activates repressor
usually anabolic
123
What is an inducible gene
## Footnote
expression
usually off
can be turned on
inducer inactivates repressor
usually catabolic
124
structural vs regulatory gene
## Footnote
expression
struct - regulated, turned on or off
reg - upstream of operon, always transcribing, codes for regulatory protein
125
Types of regulatory proteins
## Footnote
expression
all are allosteric
repressor - active form block RNAP, in operator
activator - active form enhances RNAP, in enhancer
126
What do regulatory proteins and genes to in Lac operon
| name of reg prot + type of gene, prot, effector+ name of effector
## Footnote
expression
reg gene - Lacl
type of prot - activator
type of gene - inducible
type of effector - inducer
name of effector - lactose
regulatory proteins are usually active, inducer comes in and inactivates it
catabolic
127
how is lac operon also example of positive gene reg
## Footnote
expression
for lac to turn on there must be lactose and NO glucose
cAMP get binded to Catabolite activator protein (CAP)
CAP attaches to enhancer wich helps RNAP
128
What do regulatory proteins and genes to in Trp operon
| name of reg prot + type of gene, prot, effector+ name of effector
## Footnote
expression
reg gene - trpR
type of prot - repressor
type of gene - repressible
type of effector - co repressor
name of effector - tryptophan
repressor made by reg gene usually off, when too much tryptophan it activates and represses
anabolic
129
WHat are the types of effectors
## Footnote
expression
ny molecules that regulates activity of protein
corepressor - activates repressor, stops gene expression
inducer- inactivates repressor, stops it from binding , activates gene expression, activates activator
130
What does lacZ, lacY, lacA do?
| lac operon
## Footnote
expression
catalyzes hydrolysis of lactose in bacteria
1. lacZ -> beta- galactosidase - > turns lactose into galactose + glucose (bact version of lactase)
2. lacY - > permease - > channel protein for lactose into cell
**dont need to know**
3. lacA - > transacetylase - > adds acetyl group to galactose
131
activator and repressor vs co repressor and inducer
## Footnote
expression
activator and repressor are regulatory proteins, they bind in enhancer or operator
co repressor and inducer and effectors , they bind in repressor
132
gene regulation and gene expression types
## Footnote
expression
gene reg - can be neg (repressor) or pos (activator)
gene expression - can be inducible (inducer) or repressible (corepressible)
133
In positive gene regulation how would a repressible and inducible operon look?
## Footnote
expression
regulatory protein is an activator
repressible - activators usually active, uses corepressors to inactivate (corepressor could be the product)
inducible - activators usually anactive, uses inducers (inducer could be the idk)
134
what are the 4 levels of DNA packing and size
## Footnote
euk chrom
1. nucleosome - 10 nm
2. selenoid/chromatin - 30 nm
3. looped domain - 300 nm
4. metaphase chromosome - 1400 nm
135
what are the parts of a nucleosome
## Footnote
euk chrom
DNA+ core histones
wrapped twice around 8 histones
looks like beads on a string
136
what is a histone
## Footnote
euk chrom
protein that DNA coils around to make chromatin
has pos charged R groups that bind to neg DNA groups
can be cores or linker
137
core histone vs linker histone
## Footnote
euk chrom
core - H2A, H2B, H3, H4 (used in step 1 in octomer )
linker - H1 (used in step 2, brings6 nucleosomes tgt )
138
when does supercoiling begin
## Footnote
euk chrom
on #2
when it becomes chromatic/ selenoid
139
how does supercoiling/chromosome condensation regulates gene expression/transcription
## Footnote
euk chrom
chromosome must be incoiled at region to be transcribed
wether coiled or not effects gene expression
140
what is selenoid structure, what level is it
## Footnote
euk Chrome
#2 in DNA coiling
H1 histones aggregate causing 6 nucleosomes to coil together
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What are looped domains
## Footnote
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chromatin forms loops using nonhisotne scaffolding
300 nm
3rd step
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WHat is metphase chromosome
## Footnote
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4th step in DNA coiling
occurs in mitosis
seens in metaphase
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Defintioin of gene regulation
## Footnote
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The ability to control whether a gene is actively being transcribed or not
can be structural - supercoiling
molecular - neg feedback enzymes
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euchromatin vs heterochromatin
## Footnote
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euchromatin - loose parts of chromsomes, can be transcribed
hetero - densley packed region, inactive
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When and where does methylation occur
## Footnote
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When methyl groups attach to bases (often C)
after S phase
supresses genes
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what is acetylation and its effects ?
## Footnote
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attachemnt of acetyl group to histones
activates gene expression
loosens DNA packing
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