Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cell and Molecular > L10 - Chromatin Structure and Gene Transcription > Flashcards

L10 - Chromatin Structure and Gene Transcription Flashcards

1
Q

Genetic alterations to DNA sequences

A

Permanently affect gene expression.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Epigenetic changes to chromatin structure

A 
Modulate gene expression. 
Do not alter DNA sequence
Are reversible 
Facilitate stable changes to gene expression which may persist for the life of a cell
Can be erased in the germ line
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are nucleosomes?

A

Nucleosomes can be covalently modified.
N terminal lysine rich tails (8 of them) of core histones project radially from nucleosomal core.
Covalent modifications differ between condensed inactive and open active chromatin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Types of covalent modification to core histone N-terminal tails

A
  • Acetylation of lysines
  • Methylation of lysines and arginine’s
  • Methylation/acetylation to termini lysine and serine side chains
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Histone acetyltransferases

A

Modify lysine residues
Histone code writers
Activates gene transcription

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Histone methyltransferases

A

Exhibit site specificities
Histone code writers
Represses gene transcription

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Histone deacetylases

A

Remove modification
Histone code erasers
Represses gene transcription

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Histone demethylases

A

Remove modification
Histone code erasers
Activates gene transcription

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Lysine and arginine methylation effects on gene expression?

A
  • H3-K4 active
  • H3-K9 inactive
  • H3-K27 inactive
  • H3-R17 active
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Lysine acetylation effects on gene expression

A
  • H2A active
  • H2B active
  • H3 active
  • H4 active
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does acetylation of histones create binding sites for?

A

Transcription activators that contain a bromodomain

The bromodomain transcription activator is an epigenetic code reader

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Mapping of histone acetylation across genes

A

Histone acetylation is associated with transcriptionally active promoter sequences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What does methylation of histones create binding sites for?

A

Transcriptional repressors that contain a chromodomain
Transcriptional activators that contain a PHD zinc finger domain
- Depends on the lysine amino acid residue modified

These are both epigenetic code readers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the transcriptional regulatory code?

A

An epigenetic code that lies on top of the genetic code

Governs when and where genetic information is expressed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do transcription activator proteins work?

A
  1. Nucleosome remodelling
  2. Histone removal
  3. Histone replacement
  4. Histone modifications
    • Recruitment of code writers and readers
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Activator proteins

A

Typically induce combinations of these effects.

All the effects promote RNA polymerase II recruitment.

17
Q

How do transcription repressor proteins work?

A
  1. Recruitment of chromatin remodelling complexes
  2. Recruitment of histone deacetylases
  3. Recruitment of histone methyltransferases
  4. Competitive DNA binding
  5. Masking activation surface
  6. Direct interaction with general transcription factors
18
Q

What is the Polycomb Repressive Complexes?

A

Includes proteins that can generate or recognise repressive chromatin modification

  • Histone code writing
    • H3-K27 methylation
    • Mediated by Enhancer of zeste (EZH2) component of PRC2
  • Histone code reading
    • Recruitment of PRC1 via Polycomb chromodomain
    • Formation of silent, repressed heterochromatin
19
Q

Relationship between transcriptionally repressive histone methylation and DNA methylation

A

Transcriptionally inactive promoters are rich in methylated CpG dinucleotides
Addition of methyl groups to cytosine residues is mediated by DNA methyltransferases (DNMTs)
Histone methyltransferase (EZH2) interacts with DNMTs and mutually reinforce their effects

20
Q

Transcriptionally inactive promoters are rich in?

A

Methylated CpG dinucleotides

21
Q

Addition of methyl groups to cytosine residues is mediated by?

A

DNA methyltransferases (DNMTs)

22
Q

Mammalian X-chromosome inactivation

A

Equalises levels of X-chromosome derived gene products in males and females

  • Males, XY - 1 dose of X-linked genes
  • Females, XX - 2 doses of X-linked genes
23
Q

Silencing of one X chromosome of female embryo during development

A

Initial selection of the chromosome for silencing is random
Silenced by condensation
The silencing decision is propagated clonally
- All progeny of cells in which the silencing occurred inherit the same silenced X chromosome

24
Q

Calico cat is an example of?

A

X-chromosome inactivation

25
Q

Mechanism of X-inactivation

A
  1. Xist RNA binds to the X chromosome in cis
  2. Promotes chromatin condensation –spreads away from x-inactivation centre in both directions
  3. Promotes formation of silent chromatin by recruiting histone modifying enzymes and other Polycomb group components
  4. Leads to H3K27 and H3K9 methylation of core Histones
  5. Leads to chromatin condensation and transcriptional repression  inactive X
26
Q

What is a Barr body?

A

A highly condensed inactive X chromosome at the periphery of the nucleus of female somatic cells

27
Q

Polycomb proteins role

A

Detect Xist transcripts on the X chromosome that is to be inactivated
They cause its transcriptional silencing

28
Q

Agouti mouse is an example of?

A

How dietary components can affect DNA methylation patterns which regulate phenotypes

29
Q

Calico cat genes

A 
Females:
- XO  XO : orange 
- Xo Xo: black
- XO Xo: calico
They are exclusively female
They are heterozygous for 2 alleles of an X-linked coat pigment gene
30
Q

Agouti mouse genes?

A

Agoutivy - dominant mutant allele

  • Causes obesity and yellow fur
  • Due to constitutively high expression of the agouti protein
  • Contains an insertion of an IAP element - strongly activates the agouti gene
31
Q

IAP element in Agouti mouse

A

IAP element is sensitive to DNA methylation

- High levels of methyl donors in maternal diet represses Agoutivy transcription in progeny

32
Q

Increasing levels of methyl donor molecules in diet can?

A

Rescue the phenotypic effects of Agoutivy by increasing DNA methylation which represses transcription of the Agoutivy gene

33
Q

Methylation and acetylation of some lysines are?

A

Mutually exclusive

34
Q

Mechanism of X-inactivation

A

Involves synthesis of a non-coding RNA (Xist) from the X-inactivation centre (XIC) on the chromosome destined for inactivation

Cell and Molecular (24 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions