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Biology 311C > Regulation of Gene Expression (4) > Flashcards

Regulation of Gene Expression (4) Flashcards

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1
Q

genes are regulated …

A

… by proteins that bind to regulatory sequences that are upstreams or downstreams of the transcribed sequence

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2
Q

what is the name of the units that prokaryotic genes are organized in?

A

operons

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3
Q

what are prokaryotic genes regulated by?

A

metabolites binding to proteins that recognize and bind to operators

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4
Q

where does regulation of gene expression in eukaryotes occur?

A

various levels like transcriptional, post-transcriptional, translational, and post-translational

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5
Q

what does the bacterial genome include?

A

chromosomal DNA and episomes (extrachromosomal DNA in plastids)

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6
Q

transduction

A

transfer of a part of a chromosome from one bacterium to another through a phage
- can be general or specific

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7
Q

transfection

A

experimental method to introduce dna fragments into bacterial using phage as vectors

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8
Q

transformation

A

introduction of dna from an external medium into the bacterial

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9
Q

gene expression

A

-synthesis of RNA from a DNA template
- includes translation of mRNA into specific proteins resulting in specific genotypes
- constitutive or regulated

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10
Q

constitutive genes

A

expressed without much regulation
- expressed continuously

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11
Q

Transposable elements (Transposons)

A
  • mobile genetic elements/ jumping genes
  • move from one chromosome to another part of a different chromosome
  • important in new combinations of genes, mutations, and microevolution of bacteria
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12
Q

How is bacterial dna introduced from one bacterium to another?

A

conjugation, transduction, and transformation

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13
Q

conjugation

A

sexual mating of bacterial through f-pili and the genes present in the F-factor are transferred from an F+bacteria to an F-bacteria

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14
Q

what does an operon constitute?

A
  • the coding sequences of the genes in that unit
  • a promoter
  • operator
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15
Q

what does the promoter in an operon do?

A

determine tha accuracy of transcription

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16
Q

what does the operator in an operon do?

A

determine the amount of transcription
- serves as the on/off switch to regulate transcription in response to an enviromental stimuli

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17
Q

polycistronic

A

many transcripts are made from one operon simultaneously as a single mRNA in a single transcription

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18
Q

operons can be …

A

induced (positive regulation) or repressed (negative regulation)

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19
Q

Inducible operon

A
  • mostly turned off
  • turned on only when necessary
  • present to control catabolic pathways used to break down compounds
20
Q

inductible operon example

A

lac operon
- induced when lactose is present with glucose or alone
- expression of genes for lactose-utilizing enzymes is activated by removing a repressor that is bound to the operator of the lac operon
- the lactose binds to the repressor molecule, and the operon is derepressed to start transcription
-If there is no glucose and only lactose is present, it results in an increase of cyclic AMP (cAMP) levels in the cells. The cAMP binds to a catabolite activator protein (CAP) and that binds to the promoter to further enhance the activity of the lac operon much more than the basal level at derepression alone

21
Q

repressible operon

A
  • used for anabolic pathways to synthesise compounds
  • mostly turned on
22
Q

repressible operon example

A

trp-operon to synthesize tryptophan
- the enzymes in the Trp biosynthetic pathway are expressed only when Trp is absent
- when trp is absent a repressor protein is inactive and it does not bind to the operator to repress transcription
- when sufficient levels of Trp are made, it binds to the repressor molecule and makes it an active repressor that now binds to the operator and stops transcription
- feedback inhibition at gene level

23
Q

sigma factors

A
  • can control gene regulation
  • can bind to the regulatory elements of bacteria and activate transcription
  • several types of sigma factors and other DNA-binding proteins that regulate prokaryotic gene expression
  • factors can transmit environmental signals to the genes to express the needed proteins immediately in response to the stimulus
24
Q

how is chromatin made?

A

the double helix of dna wraps around histone proteins to form nucleosomes, which condenses further to make chromatin

25
Q

Repetitive sequences

A

found near the telomere
- useful in dna replication because they fold onto themselves to provide a -OH group for dna synthesis

26
Q

gene families

A
  • result of gene replication during crossing over
  • genes essential for survival are highly duplicated
27
Q

coordinated gene expression

A

expression of multigene family members is regulated by common cis-acting elements recognized by crommon trans-acting factors specific for that gene family

28
Q

how are eukaryotic genes regulated?

A

by a set of regulatory DNA sequences/ cis-acting elements (recognized by trans-acting factors)

29
Q

in prokaryotes there are no introns to be removed (T/F)

A

T

30
Q

Where can gene expression be regulated in eukaryotes?

A

transcriptional level, translational level, posttranslational level

31
Q

the rate of transcription is regulated at the ____ level

A

gene with diff mechanisms for long and short term controls

32
Q

Long term controls (2)

A
  • compaction
  • methylation
33
Q

Compation

A
  • chromosomes condensed during cell division and later uncoil to chromatin
  • but some chromatin remain condensed and not accesible by RNA polymerase
34
Q

Methylation

A
  • to control transcription on selected chromosomes
  • by DNA methylase
  • adds methyl group to the C and A bases, preventing regions form being transcribed
  • helps DNA polymerase distinguish the old strand from the new
35
Q

short-term control

A
  • some regions of chromosomes are actively transcribed
  • some factors directly bind to RNA polymerase or other DNA binding proteins and can affect transcription through protein-protein interaction
36
Q

regulatory elements

A
  • promoter (upstream of the start site)
  • enhancers
  • repressors
37
Q

transcription factors

A
  • have unique secondary structures (motifs)
  • helix-turn (or loop) - helix proteins
  • zinc finger proteins
  • leucine zippers
38
Q

All these DNA binding proteins act as _____, which interact with each other along with these _____ (unique secondary/tertiary strictures) and with DNA to regulate _____.

A

All these DNA binding proteins act as dimers, which interact with each other along with these motifs (unique secondary/tertiary strictures) and with DNA to regulate transcription.

39
Q

Some _____ can bind to these transcription factors in the ____ and then migrate to the nucleus, bind with specific ____-acting elements, and activate the ____ of certain genes.

A

Some hormones can bind to these transcription factors in the cytoplasm and then migrate to the nucleus, bind with specific cis-acting elements, and activate the transcription of certain genes.

40
Q

Post-transcriptional regulation

A
  • limited regulation
  • alternate splicing
  • mRNA stability
41
Q

alternate splicing

A
  • during mRNA processing (where introns and exons …)
  • some exons are joined differently to yield different proteins
42
Q

mRNA stability

A
  • some mRNA are long-lived, and some short-lived
  • mRNA stability is altered by RNA binding proteins that can degrade the mRNA
43
Q

Translational regulation

A
  • in eukaryotes in the cytoplasm
  • involves initiation factors and elongation factors
  • blocks translation of processed mRNA until need arises
44
Q

Examples of translational regulation

A
  • mRNA storage
  • hormonal regulation
  • effect of cofactor on translation
45
Q

Post-translational modification

A
  • last stage of controlling gene expression at protein level
  • zymogen activation
  • selective targeting
  • chemical modification
  • glycosylation
46
Q

Totipotency

A

single-cell having the potential to become a whole new organism
- zygotes

Biology 311C (10 decks)

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