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Molecular Biology > Chromosome structure and function > Flashcards

Chromosome structure and function Flashcards

(52 cards)

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1
Q

viral genome contains:

bacterial genome contains:

A

RNA or DNA

circular

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2
Q

genetic makeup of the organism

passed from one generation to the next (conservation)

DNA replication

A

genome

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3
Q

genetic info packed into at least one very long DNA molecule

can be circular or linear

A

chromosome

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4
Q

eukaryotes have _____ chromosomes

most bacteria and archaea have _____ chromosomes

A

linear

circular

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5
Q

_________ varies widely among organisms

A

genetic distribution

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6
Q

polyploid

A

more than two types

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7
Q

describe a nucleosome

A

octamer of 2 H2A/ H2B and 2 H3/H4

146 bp of DNA and ~50bp of linker DNA

each core histone has N-terminus tail that can be modified (tails interact with other nucleosomes)

nucleosomes represent 10nm fibers

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8
Q

why are nucleosomes rich in lysine and arginine?

A

lysine has amino group at end= +

arginine = +

this occurs bc DNA is negatively charged so it allows them to interact

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9
Q

what special histone variation is found in ds breaks

A

H2A.X

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10
Q

30nm structure

role of H1

A

solenoid

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11
Q

heterochromatin vs euchromatin

A

heterochromatin

  • 700nm and
  • dense (darker stained)
  • inactive genes

euchromatin

  • less dense (lighter stained)
  • transcription going on
  • active genes
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12
Q

some regions of chromosomes are particularly rich in _________

A

heterochromatin

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13
Q

special DNA at end of chromosome that protects genes and get shortened

A

telomere

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14
Q

centromeres are _______

A

heterochromatic

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15
Q

highly repetitive DNA sequences

A

heterochromatic

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16
Q

chromatin structure affects

A

transcription
replication
recombination
chromosome transmission

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17
Q

breaking DNA and joining it to a different molecule

A

recombination

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18
Q

why do heterochromatic regions experience less recombination?

A

protects some parts of genome, like rRNA synthesis gene

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19
Q

why doesnt rRNA experience recombination

A

dont want ribosome to lose function

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20
Q

dynamic changes in ______ are key to regulation of gene activity

A

chromatin

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21
Q

what are the combination of post-translational modifications given to the histone tail

Study These Flashcards
A

acetylation, methylation, phosphorylation, and ubiquitnation

22
Q

what influence does the combination of specific modifications given to the histone tail?

Study These Flashcards
A

function or accessibility of the associated DNA region (histone code)

23
Q

what do the post-translational modifications do once modified?

Study These Flashcards
A

recruit specific proteins to the chromatin, which affects chromatin structure and function

24
Q

histone tails are ______ modified on the ______ regions that protrude from the nucleosome core region

Study These Flashcards
A

covalently

N-terminal

25
which part of the nucleosome is methylated, acetylated, phosphorylated or ubiquitinated?
N-terminus tails
26
add acetyl groups to lysine side chains
histone acetyltransferases (HATs)
27
remove acetyl groups from lysine
histone deacetylases (HDAC)
28
add methyl groups to lysine and arginine
histone methyltransferases (HMTs)
29
removes methyl group from lysine and arginine
histone demethylases
30
acetylation is associated with ______ transcription
active
31
name the two histones associated with acetylation
H3 and H4
32
which has more acetylation: euchromatin or heterochromatin
euchromatin
33
describe acetylation in lysine
acetylation removes the + charge from lysine side chains, which will affect interactions with - charge DNA
34
describe bromodomains
- histone acetylation generates these binding sites - these domains bind specifically to particular acetyl-lysnes - this protein can recruit enzymes and act on DNA - Ac-lys fits in pocket of bromodomain
35
up to how many methyl groups are added to lysine and arginine
Lys- 3 methyl groups | Arg- 2 methyl groups
36
methylation is associated with __________ of transcription
activation or repression
37
methylation of _______ in the H3 tail is associated with silent chromatin (including heterochromatin)
lysine 9
38
methylation of _______ is associated with active chromatin
H3 lysine 4
39
what determines the functional consequence of methylation
recognition of specific modifications on histones by other proteins
40
bind to any specific methylated lysines and often associated with transcriptional silencing
chromodomain | ex: HP1 protein- helps initiate heterochromatin formation in mammalian cells
41
acetylation provides additional ________
regulatory signals
42
where can histone tails be phosphorylated
serine or threonine residues
43
roles of histone phosphorylation
phosphorylation of H3 serine 10 allows cell growth transcription phosphorylation of H3 serine 10 and serine 28 correlate with chromosome condensation in mitosis
44
wide range of modification possibilities, in addition to interactivity of modifications, in which unique combos of modifications specify particular functional states of chromatin
hypothesis of histone code
45
describe ubiquitin
76 AA protein different from other chemical modifications, which adds very small groups (mainly on H2A and H2B) added by a side chain of enzymatic rxns and removed by deubiquitin enzyme
46
similar modifying protein that is similar to ubiquitin
sumo (small ubiquitin-like modifier)
47
what roles do ubiquitin and sumo have in common
transcription regulation and DNA repair
48
multi-subunit enzyme complexes that use the energy provided by ATP hydrolysis to change the positions of nucleosomes on DNA
ATP dependent nucleosome remodeling complexes
49
why does nucleosome remodeling occur?
when DNA is packaged, it presents a potential barrier to different proteins and enzymes that need to access the DNA to overcome barrier, the location of the nucleosome along the DNA can be altered in a regulated manner so that transcription can proceed
50
ATP dependent nucleosome remodeling complexes increase access to:
- sliding histone octamer along DNA - removing histone octamer and transferring it somewhere else - introducing loops into the DNA wrapped around a histone core
51
complex that disrupts nucleosome positioning
SWI/SNF complex
52
complex that helps to position nucleosomes during chromatin assembly
ACF (ISWI family)

Molecular Biology (4 decks)

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