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MCBM Exam 5 > Regulation of Gene Expression I > Flashcards

Regulation of Gene Expression I Flashcards

1
Q

What are the 2 major modifications that dictate if a region of a chromosome is active vs inactive?

A

DNA methylation

Histone modification

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2
Q

Where is DNA methylated?

A

5-methyl cystosine

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3
Q

What is chromatin composed of?

A

DNA plus all the associated proteins stuck on it

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4
Q

What is a histone?

A

Core of nucleosomes, with DNA wrapped around it

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5
Q

in eukaryotes, most genes are ___.

A

Silenced

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6
Q

What are the characteristics of the DNA and histones in heterchromatin?

A

DNA is hypermethylated at CpG dinucleotides

Histones are deacetylated

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7
Q

What are the characteristics of the DNA and histones of euchromatin?

A

DNA is hypomethylated

Histones are acetylated

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8
Q

Which is being actively transcribed, heterochromatin or euchromatin?

A

Euchromatin

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9
Q

What do histone acetyl transferases (HATs) do?

A

Unwind DNA to promote transcription

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10
Q

What do histone deacetylases (HDACs) do?

A

Reverse HATs and form nucleosomes

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11
Q

When chromatin relaxes, what results?

A

Hypersensitivity to DNase treatment

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12
Q

What does epigenetic mean?

A

Changes in phenotype without changes in genotype - Genes are the same, but only some are active in certain tissues

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13
Q

What is the gene silencing mechanism?

A

DNA methylation

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14
Q

What is the gene activation mechanism?

A

Histone acetylation

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15
Q

What are the 2 epigenetic modification activating marks that we need to know?

A

Histone acetylation of H3 and H4

Unmethylated CpG

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16
Q

What are the 2 epigenetic modification silencing marks that we need to know?

A

Histone deacetylation at H3 and H4

Methylated CpG

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17
Q

DNA methylation = ?

A

Gene silencing

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18
Q

CpG pairs have been lost from the genome over time except in ___.

A

Euchromatin

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19
Q

What does spontaneous deamination of 5-methyl cytosine yield?

A

Thymine

20
Q

CpG sites are hotspots for what?

A

Genetic mutation

21
Q

What do methylcytosines do?

A

Attract/recruit repressor proteins - directly block transcription factor from binding; may recruit other proteins to block transcription of the gene

22
Q

Histone deacetylation is a marker for what?

A

Silencing

23
Q

What regulates X-inactivation?

A

The Xist gene transcript, transcribed from the inactivated X chromasome

24
Q

What are the classic examples of genomic imprinting?

A

Prader-Willi

Angelman

25
Q

If only paternal genes are expressed, which disease is present?

A

Angelman

26
Q

What is the mutant chromosome present in Angelman?

A

Mutant maternal chromosome 15

27
Q

If only maternal genes are expressed, which disease is present?

A

Prader-Willi

28
Q

What is the mutant chromosome in Prader-Willi?

A

Mutant paternal chromosome 15

29
Q

What are the symptoms of Prader-Willi?

A 
Mental retardation
Obesity
Hypogonadism
Small hands and feet
Itchy skin
Voracious appetite
30
Q

What are the symptoms of Angelman?

A 
Mental retardation
Hypotonia
Absence of speech
Large mandible
Tongue thrusting
Epilepsy
31
Q

DNA methyltransferases uses what as the methyl donor?

A

SAM

32
Q

Which enzyme is important in silencing genes?

A

THF

33
Q

Folate deficiency during development increases the risk of what?

A

Neural tube defects

34
Q

Hyperhomocysteinuria increases the risk for what?

A

Cardiovascular disease

35
Q

What 2 things does smoking cause in genes?

A

Hypomethylation of oncogenes (increases activity of proliferation genes)
Hypermethylation of tumor suppressor genes (turns them off)

36
Q

What DNA-protein interactions are required in transcriptional regulation? (proteins)

A

DNA binding proteins

Chromatin modifiers

37
Q

What DNA-protein interactions are required in transcriptional regulation? (DNA)

A

Core promoter sequences

Enhancer/repressor DNA sequences

38
Q

What are the DNA binding proteins that regulate transcription initiation?

A

Transcription factors (TFs)

39
Q

TFs serve as recruiters for what?

A

The basal transcriptional machinery, like RNA polymerase

40
Q

Binding of TFs can increase the transcription rate of a gene by how much?

A

Many thousand fold

41
Q

What do basal factor TFs do?

A

Position RNA polymerase on the core promoter

42
Q

What do activators do? (TFs)

A

Bind to enhancer elements

Increase rate of assembly of transcriptional machinery (like NFkB, P53)

43
Q

What are the classes of TFs?

A 
Basal factors
Activators
Co-activators
Repressors
Chromatin modifiers
44
Q

Co-activators are also known as what?

A

Mediators

45
Q

What do repressors bind to?

A

Silencer elements

46
Q

What are the chromatin modifiers?

A

HATs
HDACs
HMG

MCBM Exam 5 (11 decks)

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