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Genes and early embryology > Regulation of gene expression > Flashcards

Regulation of gene expression Flashcards

1
Q

What is found on the 5’ end of pre-mRNA

A

cap

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2
Q

What is found on 3’ end of pre-MRNA

A

Poly(A)

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3
Q

What happens in eukaryotic gene expression

A

-RNA degrade or spliced to remove introns

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4
Q

What can happen to RNA other than splicing

A

Alternative splicing

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5
Q

What is alternative splicing

A

Where you remove one of the exons as well to produce one or more protein

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6
Q

Where does translation occur

A

cytosol

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7
Q

What ca happen. to RNA when in cytosol

A

Can degrade RNA or sequester in inactive form (stick it in such a way that it can’t be translated)

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8
Q

What happens afterRNA is translated

A

RNA translation hen could be degraded or made into protein + processed and then compartmentalised and secreted

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9
Q

Which type of control prevents formation of unwanted intermediates

A

Transcriptional control

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10
Q

How can there be transcriptional control (2 core mechanisms)

A
  • Binding of sequence specific transcription factors to DNA

- Control of DNA packaging and chromatin structure

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11
Q

What are cis-acting sequences

A

Eukaryotic genes are controlled by cis-acting sequences which can be close to T site or can be further away (regulatory transcription factors)

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12
Q

Where are cis-acting sequences found

A

Either proximal to transcription start site or further away

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13
Q

What are cis-acting sequences recognized by

A

Transcription factors

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14
Q

What binding sites do transcription factors have

A
  • DNA

- Transactivation domains

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15
Q

What are transactivation domains

A

Where DNA polymerase binds and is activated

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16
Q

What do transcription factors recognize

A

Discrete DNA sequence patterns

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17
Q

What are the two main parts of DNA

A
  • major groove

- minor groove

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18
Q

What do Transcription factors usually bind to on DNA and why

A

Major groove because its bigger

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19
Q

What do Transcription factors function as and why

A

Dimers because it increases binding affinity and specificity and can be homo or heterodimers

20
Q

What are the two types of transcription factors

A

General TF’s

Transcription regulators

21
Q

In a eukaryotic gene, what facilitates the binding of distal TF and the gene

A

mediator

22
Q

Why does DNA looping occur when a mediator is present

A

So that transcription factors that are far away from transcription start site can regulate transcription

23
Q

What does the mediator bind to

A

Distal and proximal TF and promoter

24
Q

Whatare the two types of DNA binding transcription factors

A
  • co activators

- co repressors

25
Q

What do co activators and co repressors do (DNA binding transcription factors)
-what does this require

A

Modify local chromatin structure to affect transcription

-requiresDNA interaction with histones

26
Q

Whats a coactivator

A

Binds and modifies chromatin

27
Q

What does a chromatin remodeling complex do

A

Unwinds nucleosome because it contains ATP

28
Q

What does a histone modifying enzyme do

A

Loss of +ve charge and so reduced interaction with phosphate backbone and so it unwinds

29
Q

Example of histone modifying enzyme

A

Histone acetyl transferase

30
Q

What does histone acetyl transferase do

A

Acetylates lysienes in histones and gets rid of positive charge so interaction with phosphate backbone weakens

31
Q

Example of a corepressor

A

Histone deacetylase

32
Q

What does histone deacetylase do

A

Reduce acetyl groups and causes binding to histones again

33
Q

different ways in which co repressors may work

A
  • methylation
  • Binds and prevents activator binding
  • Binds with activator and reacts and so activator masked
  • Single binding site on promoter and affinity for repressor is higher
34
Q

How can extracellular signals link to changes in gene expression

A
  • Activate protein synthesis f transcription factors so can regulate genes
  • Ligand binding (become active transcription factors)
  • Covalent modification (phosphorylation to activate transcription factors and dephosphorylation for inhibition)
  • Adding of second subunit (some TF’s only active as dimers)
  • Unmasking (protein bind to TF to mask signal)
  • Stimulation of nuclear entry (inhibitory protein to stop nuclear localization signal)
  • Proteolysis to release cytosolic part of TF bound to membrane to inactivate them
35
Q

What are transcription circuits used for

A

Controlling of genes

gene product can positively or negatively impact gene (i.e. positive or negative feedback)

36
Q

What is the flip flop device

A

Product of A has -ve effect on A and product of B has a -ve effect on B

37
Q

What is the feed forward loop

A

A induces B which induces c

38
Q

How to make iPS

A

Switch on fibroblasts

39
Q

Examples of transcription factors that control cell fate decisions and/or are implicated in human disease

A

Oct 4
sox 2
KIF 4
MyC

40
Q

What does the Pax transcription factor do

-If this is harmed, what can this cause

A

Controls development of neural crest cell migration

-can cause deafness, lack of iris, and eyeless embryo

41
Q

Different ways od post-transcriptional RNA modification

A
  • alternative splicing
  • RNA editing
  • mRNA stability
  • miRNA’s
42
Q

What happens in alternative pslicing

A

The Poly(A) cap is on a different place

43
Q

What happens in RNA editing

A

ApoB gene (transports lipids) needs to form low density lipoproteins in liver but chylomicrons in intestine. So cytosine deaminase converts cytosine in one of the exons to Uracil in the intestine (it is a stop codon). The protein stops at that point so chylomicron is produced there

44
Q

What is mRNA stability

A

PolyA tail and 5’ end cap loop round and bind to maintain stability. If this is disrupted then RNA is degraded

45
Q

What do mIRNA’s do

A

human genome contains non-coding RNAs and many of these are miRNAs. These associate to form RISC (RNA induced silencing complex) which either silences or reduces transcription of mRNA

Genes and early embryology (12 decks)

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