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Biol 311 > The gal yeast system and chromatin structure > Flashcards

The gal yeast system and chromatin structure Flashcards

1
Q

What can be used as a energy source is the absence of glucose by yeast?

A

galactose

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2
Q

What enzymes are involved in the import and metabolism of galactose?

A

Gal2, Gal1, Gal7, and Gal10

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3
Q

What are regulatory proteins in the yeast GAL system?

A

Gal4, Gal3, Gal80

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4
Q

If there’s no galactose are enzyme encoding genes expressed?

A

NO, Gal7, Gal10, Gal1, and Gal2 are not expressed

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5
Q

If there is galactose are enzyme encoding genes expressed?

A

YES! GAL7, GAL10, GAL1, AND GAL2 are expressed

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6
Q

Are all enzyme encoding genes in the yeast GAL system on the same dna strand?

A

NO, on different DNA strands

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7
Q

What are the three parts of the GAL4 enzyme?

A

An activation domain, a dimerization domain, and a DNA-binding domain

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8
Q

Is GAL4 a transcription factor or coregulator?

A

transcription factor as it has a DNA binding site

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9
Q

What does GAL4 bind to to initiate transcription?

A

Binds to upstream activation sequence (UAS)

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10
Q

What is UAS?

A

An enhancer sequence

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11
Q

How many UAS are upstream of all GAL genes?

A

2

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12
Q

Is GAL4 always expressed?

A

Yes, it’s always there

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13
Q

What is a repressor of GAL4?

A

Gal80

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14
Q

What other two enzymes (outside of GAL4) are always expressed?

A

Gal3 and Gal80

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15
Q

How does Gal80 repress GAL4? What is the outcome of this repression?

A

Gal3 undergoes a confirmational chnage in the presence of galactose which allows it to bind to gal80 which stops the repressor from binding to gal4. This allows the GAL4 to be active and initiate transcription

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16
Q

Define a chromatin?

A

A complex of
DNA and proteins that
make up eukaryotic
chromosomes

17
Q

Why is it harder for transcription factors to get in eukaryotic chromosomes?

A

Because chromatin is 10,000X more compact than linear DNA

18
Q

Define a nucleosome?

A

Is histones with DNA wrapped around it

19
Q

Histone octomers are composed of what?

A

Composed of 8 proteins, two of each H2A, H2B, H3, H4

20
Q

Histones are _____ charged

A

postively charged

21
Q

How does the charge of histones interact with DNA to form compaction?

A

DNA wraps around histones cause it’s overall negatively charged

22
Q

Histones contain a ______ core and flexible ________

A

folded up, tails

23
Q

What do the tails in histomes interact with?

A

Tails interact with different proteins and nearby nucleosomes

24
Q

What is the most compacted region of chromosomes?

A

Constitutive heterochromatin

25
Q

Where can we find constitutive heterochromatin?

A

in regions not transcribed

26
Q

What is facultative chromatin?

A

Type of heterochromatin, can open or close in certain conditions

27
Q

What is the open form of facultative heterochromatin?

A

euchromatin

28
Q

What are the two types of hetero chromatin?

A

Constitutive heterochromatin and facultative heterochromatin

29
Q

What two types of modification can result in chromatin modification?

A

Histone modification and DNA modification

30
Q

Where does most modification happen in histomes?

A

on tails

31
Q

What is chromatin remodelling?

A

Physically repositioning/ removing/
replacing histone octomers along
the DNA

32
Q

What is a type of histone modification?

A

acetylation

33
Q

Define histone acetylation?

A

addition of an acetyl
group to a lysine amino acid

34
Q

What are the two effects of acetylation?

A

Reduces chromatin compaction as it causes neutral charged amino acids which then loosens the interaction between histomes and DNA
Creates a binding site for a protein domain called bromodomain found in transcriptional factors

35
Q

What is the overall impact of histone acetylation?

A

increasing transcriptional activation

36
Q

What adds acetyl group to histone tail?

A

histone acetyltransferase

37
Q

What removes acetyl group from histone tail?

A

histone deacetylase

38
Q

What is the histone code hypothesis?

A

Proposes that different combinations of histone modifications specify different
transcription outcomes

39
Q
A

Biol 311 (16 decks)

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