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GN421 Exam 2 > Chromatin Structure > Flashcards

Chromatin Structure Flashcards

1
Q

What is “Fine Control”?

A

Interaction of cis-acting DNA sequences (promoters and enhancers) with RNA polymerase and transcription factors

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2
Q

What is “Course Control”?

A

Changes in structure of chromatin to prevent or enable ACCESS of RNA polymerase and transcription factors

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3
Q

What are 2 cis-acting DNA sequences?

A

Promoters and Enhancers

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4
Q

What is the difference between genome and epigenome?

A 
Genome = totality of DNA in an organism
Epigenome = totality of DNA and DNA modifications and associated proteins
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5
Q

Why is the 30nm fiber important?

A

It is the fundamental fiber of both metaphase chromosomes and interphase chromatin

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6
Q

What is the difference between 10nm fibers and 30nm fibers?

A

In the 10nm fiber, some DNA is accessible. In the 30nm fiber, most of the DNA is folded into the interior and therefore not accessible to RNA polymerase and transcription factors

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7
Q

What is the histone octamer composed of?

A

2 units each of H2A, H2B, H3, and H4

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8
Q

What is the nucleosome core composed of?

A

Histone octamer, 146 bp DNA, 1.75 turns

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9
Q

How was the nucleosome core discovered?

A

Resulted from a limit digest of chromatin by micrococcal nuclease

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10
Q

What is the main role of H1?

A

Facilitates folding of 10nm fiber into 30nm fiber

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11
Q

What is the structural difference between chromatin containing H1 vs. chromatin without H1?

A

With H1: nucleosomes have regular zigzag orientation

Without H1: beads on string

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12
Q

Describe the structure of chromatin

A

Histones on the inside, DNA on outside wrapped around the histone octamer, particulate structure

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13
Q

What did experiments with micrococcal nuclease reveal about chromatin structure?

A
  1. ) Chromatin structure may not be as uniform as thought, may be more particulate
  2. ) Less micrococcal nuclease = more nucleosomes complexed together
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14
Q

What are transgenic marker genes?

A

Genes used to determine if a piece of DNA has been successfully inserted into the genome of the host organism

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15
Q

What are selectable markers?

A

Genes that protect the transformed organism or cell from a selective agent (usually an antibiotic)

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16
Q

What is a screenable marker?

A

Genes that give transformed cells an identifiable characteristic to distinguish them from untransformed cells but do not confer resistance to the selective agent

17
Q

What are 3 examples of screenable markers?

A
  1. ) GFP: fluoresces green when excited with UV light
  2. ) Luciferase: converts energy of ATP into light
  3. ) B-Galactosidase: converts colorless substrates into colored compounds that can be easily detected
18
Q

What are reporter genes?

A

Genes usually attached to regulatory sequences of another gene of interest to test the effects of the regulatory sequence; can be used to measure gene activity

19
Q

What are insulators?

A

Boundaries between domain of the gene and the enhancer (or silencer) so that the gene can no longer feel the activating (or repressing) effects

20
Q

What are Domain Boundaries?

A

Special nucleoprotein structures formed by proteins at specific sites along chromosome

21
Q

How is inappropriate activation avoided?

A

Organisms use DNA insulators to block activation of unrelated genes by nearby enhancers

22
Q

What is the function of insulator proteins?

A

Recruit histone acetyltransferases that acetylate flanking nucleosomes; acetylation inhibits histone modifications required for the propagation of transcriptionally silent condensed chromatin

23
Q

What is the function of boundary elements?

A

To relate structural organization of chromatin fiber to informational organization of the DNA

24
Q

What are position effects?

A

The modification of gene expression when genes are relocated to new environments by rearrangement or transformation

25
Q

What is important about the site of insertion?

A

It helps determine the level of expression of the transgene

26
Q

How is repression facilitated?

A

By the association of genomic sequences with the inner nuclear lamina through lamin binding proteins

27
Q

Why are transcriptional neighborhoods (TNs) important?

A

They contain a collection of transcriptional machinery and help provide an environment for the initiation, hyperactivation, and maintenance of transcription

28
Q

What is the function of architectural proteins (APs)?

A

They bend DNA and compact chromatin

GN421 Exam 2 (7 decks)

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