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Biology 12 > Genetic mechs > Flashcards

Genetic mechs Flashcards

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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)

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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

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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

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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

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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

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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

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7
Q

What were the steps in Meselson and Stahls exp

DNA rep

A
  1. grew ecoli in heavy nitrogen (N15)
  2. transfer ecoli to lighter N14, 1 reproduction, centrifuge
  3. see 1 band (cant be conservative )
  4. 1 more replication in N14, centrifiuged
  5. see 2 bands (cant be dispersive)
    Must be semi conservative
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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)

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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)

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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

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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

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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

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13
Q

Why is priming needed

DNA rep

A

New nucleotides can only be added to the 3 end

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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

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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

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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

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17
Q

what is okazaki fragment

DNA rep

A

fragments of new DNA on lagging strand

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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

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19
Q

what is telomere

DNA rep

A

bunch of useless DNA at end of chromosome
starts with 15000 at cenception
death with 5000

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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

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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

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22
Q

What do single stranded binding proteins do (SSBPs)

DNA rep

A

binds to unwound DNA strands keeps it apart

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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

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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.

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25
Q

What does DNAP I do

DNA rep

A

replaces the RNA primers with DNA, takes place after the DNAPIII

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26
Q

if DNA nucleotides can only be added to a 3’ end, how does DNAP I add new DNA?

A

it adds it to the 3’ end of the strand before it

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27
Q

What does DNAPIII do

DNA rep

A

Adds to the 3’ end of an existing strand

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28
Q

What does DNA ligase do

DNA rep

A

Binds together the okazaki fragments after they are completely DNA
also used to bind the 2 DNA at ori
uses phosphodiester bonds

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29
Q

Eukaryote vs Prok rep termination

DNA rep

A

euk - when bubble reach another bubble, when it reaches end of DNA
prok - when it circels around to beginning of bubble

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30
Q

what is the replication problem at the end of linear DNA

DNA rep

A

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

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31
Q

what is purpose of telomeres and structure

DNA rep

A

found at end of euk chromosomes
noncoding
made from repeats of short genetic sequence
protects DNA from being eroded, getting unound

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32
Q

what is senescence

DNA rep

A

when the cell stops growing or dividing, recognizes that DNA is damaged, will not divide for protection

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33
Q

what is apoptosis

DNA rep

A

programmed self descructtion

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34
Q

what is the cellular concequence of shortened telomeres

DNA rep

A

senescence or aptosis

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35
Q

what is telomerase and what does it do

DNA rep

A

enzyme that adds telomeres to chromosomes
is a ribonucleoprotein
does reverse transcriptase

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36
Q

what is a ribonucleoprotein

DNA rep

A

protein that contains RNA in it and protein
ex human telomerase contain RNA (AAUCC)

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37
Q

what is reverse transcriptase

DNA rep

A

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 )

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38
Q

How do telomeres relate to aging

DNA rep

A

they get shorter as you age
15000 bases at conception
10 000 at birth
5000 at death

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39
Q

How the telomere is completed using telomerase

DNA rep

A
  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)
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40
Q

What cells contain telomerase acivity

DNA rep

A

germ cells and cancer cells

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41
Q

Do eukaryotes use DNAP I and III

DNA rep

A

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?

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42
Q

why does DNAP alpha make telomeres instead of DNAP III

DNA rep

A

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

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43
Q

What is a gene

Transcript

A

stretch of DNA that is transcribed into RNA
aka transcription unit

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44
Q

What is a promoter and why does it have rich AT regions

Transcript

A

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

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45
Q

transcrition initiation in euk vs prok

Transcript

A

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

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46
Q

What is coding strand

Transcript

A

strand of DNA whos base sequence is identical to the RNA
not the template

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47
Q

What is the sense strand

Transcript

A

same as the coding strand
it is the one what looks like the RNA

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48
Q

what is the antisense strand

Transcript

A

the template for the RNA
complimentary to the sense strand
does not mean anything by itself

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49
Q

What is the RNA Transcript

Transcript

A

WHat initially comes out of transcription before the post processing
primary Transcript
newly synthed RNA

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50
Q

Where does Transcript take place

Transcript

A

euk - nucleus
prok - cytoplasm

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51
Q

How do you know the 3’ end 5’ of DNA based off RNA

Transcript

A

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

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52
Q

Transcription termination for euk

Transcript

A
  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
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53
Q

transcription termination for prok

Transcript

A
  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
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54
Q

How are Transcription termination different euk vs prok

Transcript

A

prok - uses hairpin method
Euk - uses endonuclease to cut RNA off from RNAP

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55
Q

What are the types of RNAPs used euk vs prok

Transcript

A

prok - only hase 1 types of RNAP
Euk has 3 types, mainl RNAP II used

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56
Q

What is mRNA

Transcript

A

messenger RNA
final transcript, what gets translated
leaves neucleus

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57
Q

What are the 3 types of RNA processing do both euk and prok have it

Transcript

A

capping
polydenylation
splicing
only euk does this

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58
Q

What is capping (what, where, why, when)

Transcript

A

at 5’ end of new RNA
addition of modified guanine
protection from degredation, helps ribosomes bind
during transription

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59
Q

What is polyadenylation (what, where, why, when)

Transcript

A

3’ end
addition of many adenine (poly A tail)
protection, facilitation of mRNA export
after Transcription

60
Q

What is splicing (what, where, why, when)

Transcript

A

introns
intron is taken out
for alternative splicing, exon shuffling
during and after transcription

61
Q

components of splicing

Transcript

A

Splice site (on RNA)- on ends of intron, where snRNPs binds
Spliceosome - contains snRNPs+ other proteins
- snRNP - contains snRNA and protein

62
Q

What are snRNPs and what do they do

Transcript

A

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

63
Q

What are the mechinisms of splicing

Transcript

A

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

64
Q

How can splicing be recognized in a photo

Transcript

A

loops formed in the RNA

65
Q

What are introns and their function

Transcript

A

interveneing
noncoding sequences in between exons
regulate gene expression through alternative splicing

66
Q

what function of introns have direct relevence to Transcription

Transcript

A

introns can are used in alternative splicing
allows one gene to make many diff polypeptides by considering different things as introns

67
Q

What are the 4 steps in translation initiation

translate

A
  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
68
Q

prok vs euk translation initiation (compare 4 steps )

translate

A
  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
69
Q

What is shine dalgarno sequence

translate

A

prok version of 5’ cap
helps ribosome find 5’ end of prok mRNA

70
Q

what are 2 subunits and 4 binding sites in ribosome

translate

A

large top subunit, small bottom subunit
has A site, P site, E site, mRNA binding site

71
Q

What is translation initiation complex

translate

A

complete ribosome+ initiator tRNA at P site+ mRNA at AUG

72
Q

What is codon and anticodon

translate

A

codon - 3 consecutive nucleotides on RNA, codes 1 amino acid
anticod - complimentary sequence to codon on tRNA

73
Q

What are the parts of tRNA molecule and what does it look like

translate

A

is clover shaped in 2d
L shaped in 3d
3’ end holds amino acid
Anticodon is on bottom

74
Q

describe steps of translation elongation

translate

A
  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
75
Q

What is direction of reading in translation

translate

A

ribosome reads from 5’ end to 3’ end of mRNA

76
Q

Where is the C terminus and N terminus of growing peptide chain

translate

A

C terminus is where new amino acids are added
N terminus is where the start amino acid it

77
Q

How is translation terminated

translate

A

at stop codon no tRNA
release factor binds, adds water instead of amino acid
polypep gets hydrollyzed
ribosome disassebles

78
Q

How to know 5’ and 3’ end in polyribosome on RNA

also what is polyribosome

translate

A

polyribo - when 1 mRNA has many ribo translating at once
translation starts at 5’ end
translating towards DNA
closer to DNA = been translating longer

79
Q

Location of ribosome and the type of protein it produces

translate

A

free ribo (in cytosol) - makes cytoplasmic proteins (organelles)
bound ribo (right outside right endo plasmic reticulum) - makes secretory proteins (lysosomes, membrane proteins)

80
Q

Cytosol vs cytoplasm

translate

A

cytosol - fluid in the cell, organelles are within
cytoplasm - inside of cell, iincludes organelles
both exclude nucleus

81
Q

what are chaperone proteins for

translate

A

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

82
Q

What is the process of trafficking secretory proteins

7

translate

A
  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
83
Q

what is signal sequence

translate

A

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

84
Q

what is stop transfer sequence

translate

A

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

85
Q

what si SRP

translate

A

Signal recognition particle
recognizes signal sequence and takes the ribosome and everything to ER to continue translation

86
Q

waht is translocon

translate

A

like a channel protein
places where the polypep goes through to get into ER

87
Q

waht is signal peptidase

translate

A

cuts off the signal sequnce once its in the ER lumen

88
Q

What is SRP receptor

translate

A

where the signal recognition particle binds to the ER
found on cytosolic side of ER

89
Q

cell membrane proteins vs secreted proteins

compare making process

translate

A

Cell membrane proteins have stop transfer sequence, it keeps them in the ER membrane
proteins that are secreted out do not have transfer seq

90
Q

organelles in endomembrane system and their roles in protein trafficking

translate

A

Endoplasmic reticulum - folds proteins
Golgi complex - for post translational mods
lysosomes - some proteins become them
vesiclesé - transports the polypep to membrane of cell

91
Q

What are the steps in secretory system to ER

translate

A
  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
92
Q

what are all the post translational mods

translate

A

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

93
Q

What are all the ribonucleoproteins studed in this unit

translate

A

Telomerase, snRNPs, (spliceosome)
ribosomes

94
Q

What are the 3 chars of genetic code

mute

A

universal - all living things use same bases
redundant - diff codons code for same amino acid
non - ambiguous - each codon makes specific amino acid

95
Q

What is wobble hypthesis and why importance

mute

A

wobble position - third position of codon
base pairing rules are flexible there
promotes redundancy

96
Q

what is inosine and importance

mute

A

found in wobble position of tRNA
bonds with C, U, and A
allows multiple codons to make same amino acid
promotes redundancy

97
Q

spontaneous vs induced mutations

mute

A

spont - errors from replication, from enzymes
induced - from exposure to metagenic factors

98
Q

examples of physical mutegen and how

mute

A

UV light
makes pyrimandine dimers - when they bond next to each other instead of across the ladder
can be fixed, by the body usually

99
Q

```

Perymadine dimers and what is xeroderma pigmentosum

mute

A

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

100
Q

Chemical mutagen example and how it can be used benifially

mute

A

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

101
Q

Types of DNA muataions

4

mute

A
  1. chromosomal mutations (in meiosis)
  2. missing base pair
  3. fused base pair (ex. perimydine dimers)
  4. mismatch (caused by point mutation), most common type
102
Q

What is point mutation and its types (2 + subtypes)

mute

A

one nucleotide or base pair is altered
1. substitution
* transition
* transversion
2.frameshift
* insertion
* deletion

103
Q

transition vs transversion mutation also what type is it

mute

A

DNA mutation
point mutation
substitution
transition - purine to purine, perimydine to perimydine
transversion - purin to perimydine, vice versa

104
Q

when do DNA mutations occur

mute

A

in DNA replication
during S phase
Chromosomeal mutations can happen in mitosis

105
Q

insertions vs deletions + special case

what type of point mutation is it

A

DNA mutation
point mutation
frameshift
insertions - extra base is added
deletions - base is deleted
if multiple of 3 ins/del - no frameshift

106
Q

Mutation classifications for polypeptide

3

mute

A

missense
nonsense
silent

107
Q

what is missense mutation (def, where found, effect )

mute

A

type of polypeptide mutation
when RNA codes for diff amino acid
funciton may or may not change
ex. sickle cell anemia

108
Q

what is a nonsense muation (def, found where, effect)

mute

A

codes for premature stop codon
type of polypeptide mutation classification
can be lethal in embryonic stage

109
Q

what is a silent mutation (def, found where, effect)

mute

A

when mutation codes for same amino acid
type of polypep mutation
no change

110
Q

compare diff mutation effec ton polypep

mute

A

transition, transloc, - missense, nonsense, can be silent
insert or delete - extensive missense, nonsense, never silent
no frameshift, ins/del: missense, nonsense , never silent

111
Q

1.

2 ways to repair DNA from mutation

mute

A

endocuclease- repairs DNA outside of rep
exonuclease - proof read as DNA is rep

112
Q

exo vs endo nucleas repair

mute

A

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)

113
Q

Steps in NER and enzymes used

mute

A

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

114
Q

why is antibiotic resistant pos even though its not good for humans

mute

A

its relative
its good for the thing that got the mutation, bacteria

115
Q

if mRNA has 27 codons, how many amino acids in polypep?

mute

A

26
the met (start codon) is taken out?

116
Q

pos vs neg gene regulation

+ ex

expression

A

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

117
Q

what is operon

expression

A

a groupd of genes that share a single promoter
code for things with related functions

118
Q

What are components of operon

expression

A

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

119
Q

monocistronic vs polycistronic

expression

A

mono - in euks, promoter controls 1 gene
poly - in prok , genes with related funcitons tgt, one promoter for many genes

120
Q

What is a constitutive gene

expression

A

regulatory genes/housekeeping genes
always transcribing
upstream of operon
unregulated

121
Q

What is a repressible gene

expression

A

Usually on
can be turned off
corepressor activates repressor
usually anabolic

122
Q

What is an inducible gene

expression

A

usually off
can be turned on
inducer inactivates repressor
usually catabolic

123
Q

structural vs regulatory gene

expression

A

struct - regulated, turned on or off
reg - upstream of operon, always transcribing, codes for regulatory protein

124
Q

Types of regulatory proteins

expression

A

all are allosteric
repressor - active form block RNAP, in operator
activator - active form enhances RNAP, in enhancer

125
Q

What do regulatory proteins and genes to in Lac operon

name of reg prot + type of gene, prot, effector+ name of effector

expression

A

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

126
Q

how is lac operon also example of positive gene reg

expression

A

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

127
Q

What do regulatory proteins and genes to in Trp operon

name of reg prot + type of gene, prot, effector+ name of effector

expression

A

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

128
Q

WHat are the types of effectors

expression

A

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

129
Q

What does lacZ, lacY, lacA do?

lac operon

expression

A

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

130
Q

activator and repressor vs co repressor and inducer

expression

A

activator and repressor are regulatory proteins, they bind in enhancer or operator
co repressor and inducer and effectors , they bind in repressor

131
Q

gene regulation and gene expression types

expression

A

gene reg - can be neg (repressor) or pos (activator)
gene expression - can be inducible (inducer) or repressible (corepressible)

132
Q

In positive gene regulation how would a repressible and inducible operon look?

expression

A

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 )

133
Q

what are the 4 levels of DNA packing and size

euk chrom

A
  1. nucleosome - 10 nm
  2. selenoid/chromatin - 30 nm
  3. looped domain - 300 nm
  4. metaphase chromosome - 1400 nm
134
Q

what are the parts of a nucleosome

euk chrom

A

DNA+ core histones
wrapped twice around 8 histones
looks like beads on a string

135
Q

what is a histone

euk chrom

A

protein that DNA coils around to make chromatin
has pos charged R groups that bind to neg DNA groups
can be cores or linker

136
Q

core histone vs linker histone

euk chrom

A

core - H2A, H2B, H3, H4 (used in step 1 in octomer )
linker - H1 (used in step 2, brings6 nucleosomes tgt )

137
Q

when does supercoiling begin

euk chrom

A

on #2
when it becomes chromatic/ selenoid

138
Q

how does supercoiling/chromosome condensation regulates gene expression/transcription

euk chrom

A

chromosome must be incoiled at region to be transcribed
wether coiled or not effects gene expression

139
Q

what is selenoid structure, what level is it

euk Chrome

A

2 in DNA coiling

H1 histones aggregate causing 6 nucleosomes to coil together

140
Q

What are looped domains

euk Chrom

A

chromatin forms loops using nonhisotne scaffolding
300 nm
3rd step

141
Q

WHat is metphase chromosome

euk Chrome

A

4th step in DNA coiling
occurs in mitosis
seens in metaphase

142
Q

Defintioin of gene regulation

euk chrome

A

The ability to control whether a gene is actively being transcribed or not
can be structural - supercoiling
molecular - neg feedback enzymes

143
Q

euchromatin vs heterochromatin

euk chrome

A

euchromatin - loose parts of chromsomes, can be transcribed
hetero - densley packed region, inactive

144
Q

When and where does methylation occur

euk chrome

A

When methyl groups attach to bases (often C)
after S phase
supresses genes

145
Q

what is acetylation and its effects ?

euk chrome

A

attachemnt of acetyl group to histones
activates gene expression
loosens DNA packing

146
Q
A

Biology 12 (8 decks)

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