Chapter 12: The Control of Gene Expression Flashcards Preview

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Flashcards in Chapter 12: The Control of Gene Expression Deck (43)
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Proteasome does what?

- chops up polypeptide if something is wrong ( one way of going about controlling gene expression)


Organization of a bacterial operon: What is a promoter?

- DNA sequence that promotes transcription


Organization of a bacterial operon: How does a promoter, promote transcription?

- it is where the polymerase will bind and or the activator to help out in the promoter region all to enhance the probability of transcription to occur.


Organization of a bacterial operon:

Operator region? L> repressor protein?

- it is located somewhere in the gene itself it can be in the promoter by the promoter...and generally it is a sequence of DNA that will bind to a repressor protein turning it off...aka preventing transcription. Generally the repressor protein is a protein that was transcribed and translated on its own somewhere else to one and bind to this regulatory region


Lac operon

- it is what kind of an operon?

- inducible


Lac operon

- lactose used by bacteria in the absence of?



Lac operon

- What genes are involved?

- Lac Z, Lac Y, Lac A


When is the lac operon transcribed?

- decreasing levels of glucose in the bacterial medium causes a cellular response

- increase in cAMP+ - intracellular cAMP binds to CAP(catabolite activator protein) and this complex binds to DNA:

- CAP binding site

- RNA polymerase is able to bind to promoter IF lactose is present in the medium

- lactose will bind to and inactivate the lac repressor ***

- dual operator control....CAP acts as an activator and the negative control: the lac repressor that turns it off.


Inner workings of the Lac operon:

- lactose binds to?

- active lac repressor

- RNA polymerase is now able to bind to promoter


Control Region of the Lac Operon:

- Describe the structure of it 

- Promoter region= cAMP-CRP binging site, RNA Polymerase  binding site and the first part of the operator. 

- operator region 

L> mRNA?

- I gene 

- Z gene 


Lac operon: 

- Describe induced state

-structural genes (Z, Y, A) 

- transcription of those  via RNA polymerase 

-mRNA is produced

-goes through translation via polyribosomes 

- produces enzymes 

-the enzymes can utilize lactose via catabolic pathway causing the concentration of lactose to fall as it is degraded...the operon will enter a repressed state due to this 


Lac Operon: 

- describe the repressed state

- as concentrations of lactose go down via it being degraded by the enzymes produced from the lac operon ...the operon will enter a repressed state 

- this state blocks transcription via something blocking the operon from being transcribed 



Eukaryotic Gene Repressor proteins:

- three scenarios ?

1. competitive DNA binding

- fight between activator (repressor for binding site (overlap).

2. Masking activation surface

- repressor/activator both bind, but activator surface is pressed

3. Direct interaction with general transcription factors


Silencing Genes:

-____ level of control

- transcriptional


Silencing Genes:

- Now active genes are?

- silenced


Silencing Genes:

- methylation of?


-CG sequence: CCGG or GGCC

- inherited in progeny cells


Silencing Genes:

- what checks the CG sequence?

- maintenance methylase checks CG sequence


Silencing Genes:

- binding of ___ that recognize ___.

- proteins

- methyl C


Silencing Genes:

- Complexes?

- Chromatin remodelling complex, histone complex bind/activate.


Silencing Genes:

- 1/100000 nucleotides ___. Is this universal in eukaryotes?

- methylate

- no


Silencing Genes:

- The replication fork, methylates ?

- daughter strand by copying methylation on parent strand.


Silencing Genes:

-Symmetrical sequence?

- methylates after transcription...ONMT1 protein travels with


Alternative Splicing:

-this allows you to obtain what?

- different proteins from a single RNA transcript


Alternative Splicing:

-shorter antibodies result released in blood (ex:IGM) - hydro_?



Alternative Splicing:

-They are longer in?

- membranes of infected cell, hydrophobic


Alternative Splicing:

- RNA editing?

- RNA made, maybe processed, enzyme only affects


Alternative Splicing:


- New splice sites


-new stop codons - amino acid substitutions


Negative Translational Control:

- ___ sequence in prokaryotes

- Shine-dalgarno sequence

- six conserved nucleotides (GGAGGA)

- upstream AUG

- correctly position RNA initiating codon with small ribosomal subunit


Negative Translational Control:

- involves what?

- Blocking the shine dalgarno sequence by a translational repressor protein.


Negative Translational Control:

- EIF2?

- eukaryotic activation (initiation) factor brings in initiator tRNA, phosphorylated, can't bring in initiator