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Cell & Molecular Biology > Gene expression (lectures 10 - 11) > Flashcards

Gene expression (lectures 10 - 11) Flashcards

1
Q

Why is gene expression regulated?

A
  • helps microorganism used available nutrients
  • cell differentiation is driven by gene expression
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2
Q

What are the 2 types of genes (in terms of gene expression)?

A
  • continuously expressed gene (house keeping genes)
  • inducible genes (only expressed at certain times)
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3
Q

What are the 2 types of mutations?

A
  • Cis-acting mutations
  • Trans-acting mutations
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4
Q

What are Cis mutations?

A

Mutation within the same gene

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5
Q

What are trans mutations?

A

Mutations in a different gene

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6
Q

What do cis mutations identify?

A

DNA/RNA sequences

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7
Q

What do trans mutations identify?

A

Protein or RNA factors that regulate gene expression

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8
Q

At what stage of protein synthesis does gene regulation occur?

A

Transcription level

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9
Q

What is the reason that transcriptional regulation occurs at the transcriptional level?

A

Limits wasteful production of biomolecules that aren’t needed

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10
Q

What is the name given to trans acting factors that cause activation?

A

“trans-acting activators”

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11
Q

What is the name given to trans acting factors that cause down regulation?

A

trans-acting repressors

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12
Q

At what location do activators promote gene expression?

A

Weak promoters

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13
Q

What do activators in E. coli bind to in order to promote DNA binding?

A

The a-subunit of RNA polymerase

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14
Q

E.coli gene promoters have conserved bipartite sequences. What does this mean?

A

Sequence which consists of 2 sequence blocks

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15
Q

What can enzyme coding genes be regulated by?

A

Substrate availability

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16
Q

What is the name given to substrates that upregulate enzyme activity?

A

Inducers

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17
Q

What is the name given to substrates that down regulate enzyme activity?

A

Corepressors

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18
Q

How can different type of pre-mRNA splicing affect the protein being produced?

A

There may be a productive & a non-productive pathway. The productive splicing pathway, may lead to a productive protein being created, whereas, the non-productive pathway will not.

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19
Q

What type of proteins are used to determine exon inclusion or exclusion?

A

Splicing activator or repressor proteins

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20
Q

Define global regulation? (think growth)

A

An upregulation of all transcription as growth is stimulated

21
Q

What is gene expression autoregulation?

A

The gene product influences its own expression.

22
Q

What type of proteins in E.coli can bind to their own mRNA (gene expression autoregulation)?

A

Ribosomal proteins

23
Q

What post-translational process can regulate post-translational modification?

A

Phosphorylation (of serine, threonine or tyrosine - all have alcohol side chain)

24
Q

What is post-translational phosphorylation driven by?

A

Protein kinases

25
Q

What can reverse post-translational phosphorylation?

A

Phosphates

26
Q

What 3 structural genes are encoded by the lac operon?

A

Lac Z, Lac Y, Lac A

27
Q

What type of metabolism is associated with the Lac operon?

A

Lactose metabolism

28
Q

What is the regulatory gene on the lac operon?

A

LacI

29
Q

What is the operator gene on the lac operon?

A

Lac O

30
Q

Lactose is a disaccharide of what 2 monosaccharides?

A

glucose & galactose

31
Q

What enzyme breaks down lactose?

A

lactase (B-galactosidase)

32
Q

What is the preferred sugar for metabolism?

A

glucose

33
Q

What causes lactose intolerance?

A

An inability to metabolise lactase

34
Q

How many subunits does the lacl repressor have?

A

4

35
Q

What are the 2 molecules that the lacl repressor can bind to?

A
  • DNA (promoter region)
  • lactose
    (BUT NOT AT THE SAME TIME)
36
Q

When glucose & lactose are both present, which is the preferred source for metabolism?

A

Glucose

37
Q

What is the diauxic growth curve?

A

A curve which shows how glucose is metabolised, followed by a plateau, before lactose metabolism.

38
Q

What is catabolise repression?

A

Phenomenon by which the metabolism of lactose is repressed until the metabolism of glucose is complete.

39
Q

How does the catabolise repression blocks the lac operon?

A

Adenylate cyclase & catabolite activator protein (CAP) inhibit expression of the lac operon.
1. cAMP is produced by adenylate cyclase, however it is inhibited by the presence of glucose.
2. This prevents the cAMP/CAP complex forming and therefore doesn’t bind to the CAP site, which prevents RNA polymerase activity.

40
Q

What is the role of elF2 (eukaryotic initiation factor 2)?

A

Bind to initiator tRNA & bring it to the small ribosomal subunit.

41
Q

What does the eIF2 do once the initiation codon has been localised?

A

eLF2 hydrolyses GTP to GDP

42
Q
A
43
Q

What is needed for eIF2 to convert GTP to GDP?

A

GTPase activating proteins (GAPs)

44
Q

What is needed to recycle GTPase?

A

Guanine exchange factor (GEF) is needed to convert GDP back to GTP.

45
Q

What is the integrated stress response?

A

The reduction of global translation in response to various stress signals

46
Q

How does the body reduce global translation?

A

Reduces the the pool of eIF2, which therefore limits the level of translation that can occur.

47
Q

What happens if eIF2 is phosphorylated?

A

It turns into eIF2B, which is an inhibitor.

48
Q

What is eIF2B?

A

An inhibitor of translation

49
Q
A

Cell & Molecular Biology (20 decks)

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