summarised notes for 6.1.1 cellular control
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6.1.1 cellular Mark Scheme points
control
a) Types of Types of mutation:
gene Substitution- a base is replaced by another base,
mutations the effect depends on the base substituted, may
and their have a neutral effect.
possible Insertion- a DNA base is inserted leading to a
effects on frame shift.
protein Deletion- a DNA base is removed leading to a
production frame shift.
and function Possible effects:
Beneficial- possibility of a mutation given bacteria
or pests resistance to antibiotics or pesticides.
Harmful- mutated pathogens antigens shape
changes so become resistant to vaccines.
A frame shift changes all triplets downstream
therefore a different amino acid sequence therefore
a different tertiary structure.
Neutral – due to the degenerate nature of DNA
some triplets code for the same amino acid
therefore the amino acid sequences are not altered.
The mutation could occur in an intron (non-coding
region).
b) Regulatory Transcriptional level
mechanism Lac operon
s that A cluster of genes (lACA, LACZ, LACY).
control gene Allow the uptake and digestion of lactose in E. coli
expression bacteria.
at the When lactose is present, lactose binds to the
transcriptio repressor protein.
nal level, this changes the shape of the protein which
post- prevents it from binding to the operator.
transcriptio RNA polymerase can bind to the promotor.
nal level lacZ and lacy are transcribed into mRNA.
and post- Transcription factors in eukaryotes
translational A hormone binds to and activates transcription
level factors.
TF binds to promotor region, enabling RNA
polymerase to bind.
Can be coded for by regulatory genes.
Switch structural genes on/off controlling gene
expression.
Post-transcriptional level
Editing of primary mRNA.
The removal of introns to produce mature mRNA.
Alternative splicing produces different versions of
mRNA.
Post-translational level
Activation of proteins by cAMP
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