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MCBM Exam 5 Kat > Gene Regulation I > Flashcards

Gene Regulation I Flashcards

0
Q

How does positive regulation make more sense in highly differentiated cell systems?

A

Most genes are off until needed making fine control easier in huge genomes like ours.

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1
Q

What happens to most eukaryotic genes?

A

They are silenced

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2
Q

Why is heterochromatin not transcribed?

A

This is because the DNA is hyper methylated at CpG nucleotides and their histones are deacylated

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3
Q

Why is euchromatin transcribed?

A

It’s DNA is hypomethylated and it’s histones are acylated

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4
Q

How are histones modified when being transcribed?

A 
Histone acetyl transferases (HATs) unwind DNA to promote transcription
Histone deacetylases (HDACs) reverse the process to form nucleosomes
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5
Q

What happens to chromatin overall when being transcribed?

A

Chromatin relaxes, resulting in hypersensitivity to DNase treatment

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6
Q

What is DNase treatment?

A

CpG islands

Hpall Tiny Fragments or HTF islands

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7
Q

What does PCAF do?

A

It’s a HATs

Acetylates residues in H3 and H4

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8
Q

What does NuA4 do?

A

Acetylates H2A and H4

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9
Q

What does SWI/SNF do?

A

Nucleosome movement; transcriptional activation

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10
Q

What does the ISWI family do?

A

Nucleosome movement; transcriptional repression

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11
Q

What does epigenetic refer to?

A

Changes in phenotype without changes in genotype “heterochromatin vs euchromatin”

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12
Q

What does DNA methylation do?

A

Gene silencing

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13
Q

What does histone acetylation do?

A

Gene activation

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14
Q

What are CpG’s considered to be?

A

Hotspots for genetic mutation

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15
Q

What do methylcytosines attract?

A

Repressor proteins

16
Q

How to methylcytosines attract repressor proteins?

A

MeC in enhancer blocks transcription factor binding directly
MeC recognized by MBP, which recruits co-repressor (transcription block)
Recruited co-repressors include chromatin modifiers (HDACs, HMTs)
Intragenic methylation truncates transcription

17
Q

What regulates X-inactivation?

A

By the Xist gene transcript, transcribed from inactivated X chromosome

18
Q

What is the Xist gene?

A

A large (17kb) polyadenylated transcript with no large ORF… No protein product

19
Q

What happens to Xist once the X chromosome is inactivated?

A

Xist remains in nucleus & associates with inactivated X

20
Q

What makes deletion in region 15q11-13 different than others?

A

The genes are differentially silenced in male and female gametes

21
Q

What is Angelman syndrome?

A

Only paternal genes are expressed meaning there was a mutant maternal chromosome 15

22
Q

What is Prader-Willi syndrome?

A

Only maternal genes are expressed meaning there was a mutant paternal chromosome 15

23
Q

What are the symptoms of Prader-Willi syndrome?

A 
Mental retardation
Obesity
Hypogonadism
Small hands & feet
Itchy skin
Voracious appetite
24
Q

What are the symptoms of Angelman Syndrome?

A 
Mental retardation
Hypotonia
Absence of speech
Large mandible
Tongue thrusting
Epilepsy
25
Q

What does folate deficiency affect during development?

A

Increases risk for neural tube defects

26
Q

What does hyperhomocysteinuria increase risk for?

A

Increases risk for cardiovascular disease

27
Q

What are some epigenetic changes that cigarette smoke causes?

A

Hypomethylation of oncogenes

Hypermethylation of tumor suppressor genes

28
Q

What are the two basic classes of genes?

A

Constitutive - essential for cell survival

Inducible/repressible - highly regulated

29
Q

What are transcription factors?

A

DNA binding proteins that regulate transcription initiation

30
Q

What do transcription factors do?

A

Recruiter for basal transcription machinery

Enhance speed and efficiency of RNA polymerase

31
Q

How much can transcription factors increase the transcription rate by?

A

By many thousand full

32
Q

What are basal factors? And what are some examples of them?

A

A transcription factor that positions RNA polymerase on the core promoter

TFIID,A,B,E,F,&H

33
Q

What are activators?

A

Transcription factors that bind to enhancer elements; up rate of assembly of transcriptional machinery

34
Q

What are mediators?

A

Adapter molecules that connect activators (&repressors) to basal factors

35
Q

What are repressors?

A

Transcription factors that bind to silencer elements; interfere with activators to slow transcription or induce heterochromatin formation

36
Q

What are 3 heterochromatin modifiers?

A

HATs, HDACs, HMG proteins

MCBM Exam 5 Kat (15 decks)

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