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Biology > 1.15. Epigenetics > Flashcards

1.15. Epigenetics Flashcards

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1
Q

acetyl group (with and without)
- acetic acids (CH3-COO^-)

A
  • abundant in the nucleus
  • with AC - histone tails don’t join together, don’t pull histones closer so level of DNA condensation decreased, increasing gene expression
  • without AC (normal) - histones pulled together, higher level of DNA condensation, reduction in gene expression
  • it impacts the conformation of histone tails and therefore impacts the expression of genes
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2
Q

modification of histone tails by acetyl groups

A

acetylation

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3
Q

epigenetics

A

set of instructions that sit down on the DNA and histones - the chemical environment of the DNA impacts the gene expression

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4
Q

genome (DNA)
proteome (proteins)
transcriptome (mRNA)
___

A

epigenome (all epigenetic marks of an organism - e.g. alcohol, Me CH3- and Ac CH3COO-)

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5
Q

acetylation of…
methalanation of…

A

histone tails
the DNA

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6
Q

epigenetic marks

A

small chemical tags that sit down on the chromosomes and tell the DNA whether to compact or not - the tell the cell wat to do/who to become by controlling the expression of genes: they can condense chromatin (turn some genes off) or stretch it (make genes accessible)

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7
Q

total length of a single cell’s DNA is ___, and the length of the nucleus is ___.

A

2 meters, 0.0004 cm (around 4 micrometers)

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8
Q

chromatin (definition and role)

A

combination of DNA and histones - fitting the DNA in the cell nucleus - gene expression reduction

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9
Q

how are cell differentiation and epigenetics connected

A

selective positioning of epigenetic markers tells certain cells which genes to turn off and which to turn on (cell differentiation is irreversible)

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10
Q

genotype -
phenotype -

A

all genes of an organism
only expressed genes of one cell (e.g. genes for eyes - contain unexpressed gene for blue eyes)
- all cells of the same organism have the same genotype but different phenotype (different sets of genes activated)

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11
Q

Epigenetics mars are laid down on the cell’s genome during…

A

…embryonic development (most of it)

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12
Q

On what does laying down of epigenetic markers depend on?

A

on surrounding cells (they receive signals from other cells and epigenetic markers accumulate) and environment outside of the embryo (food, stress, air… also give out signals for the markers)

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13
Q

transgenerational epigenetic inheritance

A

epigenetic mark,s can be transmitted to multiple generations (over tens of generations)

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14
Q

epigenetic marks are…

A

reversible (can be removed from genes - medicine, environmental factors, psychological factors…)

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15
Q

cancer treatment and epigenetics

A

tumor-suppressor genes have marks on them that can deactivate them - if epig. marks are removed they can protect the cell and prevent formation of cancer cells or restore them to normal cells

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16
Q

the process that turns genotype to phenotype is ___

A

gene expression (transcription, translation, protein function (post-translational modification))

17
Q

control of gene expression usually happens…

A

at the level of transcription - how much of a specific protein will be produced

18
Q

transcription and translation can happen simultaneously…

A

in prokaryotes (both in cytoplasm, no post-transcriptional modification)

19
Q

how can gene expression be controlled

A
  • lifespan of mRNA can be regulated - regulation of translation (short-living molecules, same as proteins)
  • external factors can regulate it
20
Q

repressor

A
  • prevents transcription (RNA polymerase cannot bind to promotor region)
  • opposite of activator (it promotes transcription)
21
Q

TATA box (TATAAAA sequence)

A

part of promotor where DNA binding proteins (general transcription factors) specifically bind, indicating to RNA polymerase where transcription should start
- only in eukaryotes

22
Q

upstream from the promotor region lie…

A

two regulatory sequences: silencer and enhancer

23
Q

promotors are ___ for genes, silencers, and enhancers are ___ for genes

A

similar, unique

24
Q

silencer and enhancer

A

binding sites for specific transcription factors: repressor (repressing transcription) and activator (promoting transcription)

25
Q

if repressor binds to silencer…

A

RNA polymerase cannot attach to the promotor region and transcription is impossible (vice versa with activator binding to enhancer region)

26
Q

regulation of mRNA lifespan

A
  • poly A-tail shortens with each translation and the rate of its shortening determines how long mRNA persists
  • various factors impact the length of the poly A-tail and therefore the longevity of mRNA
27
Q

example of regulation of mRNA lifespan

A

egg laying animals:
- protein vitellogenin is a precursor of egg yolk
- high estrogen levels increase the longevity of mRNA that encodes for vitellogenin and high-quality egg yolk (eggs) are formed
more estrogen = better yolk (longer mRNA lifespan)

28
Q

poly A-tail can be…

A

regenerated

29
Q

external factors regulating gene expression

A
  • bacterium E. coli (heterotrophic organism - merging simple inorganic substances into organic (glucose))
  • can utilize lactose from the medium but needs lactase
  • lactase synthesis is inducable: regulated by the presence/absence of lactose
  • lactose impacts the gene expression of the gene for lactase
30
Q

poly A-tail protects the mRNA so that…

A

the same mRNA can be transcribed multiple times

31
Q

gene regulator (E. coli)

A

produces repressor protein (it is a coding region of the DNA that gets transcribed)
- constantly getting transcribed

32
Q

operator (E. coli)

A

before the lactase gene - it is the binding site of the repressor protein (ON/OFF switch for the lactase gene)

33
Q

what happens of lactose is present (E. coli)

A

lactose molecules join with the repressor protein and change its conformation so that it can no longer join with the operator - nothing preventing RNA polymerase from sliding and transcribing the lactase gene - lactase digests all lactose - gene can no longer be expressed - cell doesn’t want to waste E on producing E when there is no S

Biology (45 decks)

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