Summary
OCR A-Level Biology Cellular Control(1) Summary
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Handwritten Summary by an Oxford Medical Student which covers all content necessary for an A* in Cellular Control at OCR Biology A-Level.
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Transcriptional Control :Genes can be turned on or off
Chromatin Remodelling :
·
Heterochromatin :
Tightly Wound DNA - cannot be transcribed
·
Euchromatin :
Loosely wound DNA in interphase ->
Can be transcribed
↳ histones
Acetylation :
makes the more
negative ,
DNA is loosened
Methylation makes the histones more
hydrophobic DNA coils more
tightly
:
,
Lac Operon
group of genes that are controlled by the same regulatory mechanism
:
A
1
Regulatory gene Codes for a repressor Regulatory Gene Promoter /Operator /Genes
.
.
.
2
Repressor protein binds to the operator and prevents ~Represso :
RNA
polymerase from binding to the promoter
In the presence of lactose :
: Codes for a repressor Regulatory Gene Promoter /Operator /Genes
Regulatory gene RNA
.
7
2 Lactose binds to the repressor protein,
Polymerase
transcription
causing
.
lactose
it to
change shape Repressor
.
3 The repressor bind to the operator
can no
longer
4 RNA can now bind to the promoter
polymerase
.
Cyclic AMP :
post-transcriptional/Pre-translational Control :
RNA added to the S'end
processing Cap is Stabilise mRNA
·
:
7
·
Tail is added to the 3' end
Delay degradation
·RNA
editing Splicing of introns -> Non zoding DNA
:
.
Translational Control :
Degradation of mRNA molecules last
·
more resistant
longer < more proteins
:
·
Binding of inhibitory proteins to mRNA
Initiation factors Aid the
binding of mRNA to ribosomes
:
Protein kinases
Catalyse the addition of phosphate groups to proteins Activates
·
enzymes
:
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