Summary OCR A Level Biology A* Cellular Control Detailed Notes
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Course
Module 6 - Genetics, evolution and ecosystems
Institution
OCR
These A-Level Biology notes are designed for students aiming for top grades and a future in medicine. They are both aesthetic and detailed, offering comprehensive coverage of the syllabus while being visually engaging.
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b deaminating cheminals can convert onebaseintoanother c methyl ethyl groupscauseincorrect barepairing
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d viruses caninsert sections of DNA into cellularDNA
and a
most mutations have no effect a don'tslightly change poyptph.de sitturedittin.tn
affair
OR b mutation in non coding region no effect on basesequence
insertion deletion of nucleotides changes aminoacid that wouldhavebeencoded for are
noaiterentiodonofbases frameshift mutation causes knock on effect to baseswiner along
DNA sequence changes amino acid sequence produced polypeptide'sability to function
substitution of nucleotides DNAbase randomly swapped for another 3waysrooms
siren
m an c.net.inei siatnti etm iniini i
alter a single amino acid in polypeptide e g silkle cell anaemia 3 Nonsense
mutations create a premature stop codon Ishops mRNA translation incomplete polypeptide alters
structure function of protein
effect on polypeptides mutations are either I Benefirial 2 Harmful 3 Neutral
Benetitial some result in slightly altered polypeptidewith differentshape differentabilityto perform its
notion improves e g betterabivingof activesite to bind to substrate or bettershengm instructuralp rovei
g melanin production in early humans in Africa protects fromharma Uv radiation decreased as
humans moved north mutation so could synthesise vitamin D more easily preventing rickets
Harmful e g manygenetic diseases haemophilia sicklecell anaemia cysticfibrosis nausea bydeletion
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unction or c resultingailterence in characteristic has no advance.gg
althoughnucleusof every cell contains thesame genes not an genes are expressed in all cells all the time
djeadyg
regulatory mechanisms ensurecorrect genes are expressed in correctcell at correct time controlled byregulatorygen
3maintypes 1 transcriptional during wanscription 2 post transcriptional Cattertranscription 3 post wansiatio
structural genes code for a protein with function INSIDE cell enzymes carrier hormone VS regulatory
genes node to proteinthat controls expression of
structural genes levels of protein production candomultiple
1.3 Genecontrol Lac operon regulatory mechanism at transcriptional level
operon a cluster of structural genes in prokaryotescontrolled by thesame promoter
lar operon in bacteria control productionofenzyme lactate B galactosidase matbreak downlacto
and 2 other structural proteins as an energysource inducibleenzyme onlysynthesised when
promoter needed sectionofDNAto wanscription lactose is present prevents was
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regulatory gene coding for lac repressorprotein this has 2 bindingsires so it can bindto
a operator to preventtranscription ofsavewalDNA RNA polymerase can't attachto promoter
b lactose electron molecule shapeof repressorproteindistorts can'tbindto operator
whenlactose is absent I Regulatory genetranscribed translated 2 lacrepressor
protein produced 3 Lacrepressorprotein binds to operator regionbefore lacz a RNA
polymerase can't bind to promoterregion transcription iantoccur dueto presence of
repressorprotein s 6 Nolactatesynthesised
no transcription of structural genes
when lactose is present 1 Bacteria uptakes lactose 2 Lactosebinds to second
binding site onrepressorprotein distorts itsshape can'tbindto operator 3 RNA
polymerase can bindto promoter transcription occurs 4 mrna translatedfromall
structural genes s lactaseenzymeproduced C lactose can bebrokendownforenergy
1 4 Gene control transcription Factors
transcriptionfactors controlgene expression ineukaryotes win about 10 of humangenes coding forthem
some bindto promoterregion of a gene to allow prevent transcription
estrogen controls the oestrus cycle andsperm production I In
the
estrogenislipidsolubleso distures through plasma membrane ofcell nucleus 2 binds to a receptor containedwithin
a protein complex 3 receptorchanges shape moves awayfromprotein complex attaches topromoterregion
oftargetgene a attractsother cofactors to bind with it enablesRNA polymerase to transcribetargetgene
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