Understanding Gene expression is regulated by proteins that bind to specific base sequences in DNA The environment of a cell and of an organism has an impact on gene expression Nucleosomes help to regulate transcription in eukaryotes ID: 402408
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7.2 Transcription and gene expression
Understanding:Gene expression is regulated by proteins that bind to specific base sequences in DNA The environment of a cell and of an organism has an impact on gene expressionNucleosomes help to regulate transcription in eukaryotesTranscription occurs in a 5’ to 3’ direction Eukaryotic cells modify mRNA after transcription Splicing of mRNA increases the number of different proteins an organism can produce
Applications:The promoter as an example of non-coding DNA with a function
Skills:Analysis of changes in DNA methylation patterns
Nature of science:
Looking for patterns, trends and discrepancies: there is mounting evidence that the environment can trigger heritable changes in epigenetic factorsSlide2
Applications:
The promoter as an example of non-coding DNA with a function
Not all DNA codes for a polypeptide to be madeMay have another useful functionNon-coding sequences of DNAExample: Promotor
CodingNon CodingNon coding DNASlide3
Applications:
The promoter as an example of non-coding DNA with a function
Located near a gene Binding site of RNA polymeraseInitiates transcriptionPromoters are not transcribed into RNASame sequence for most genes (general RNA polymerase binding)
PromotorsSlide4
Some proteins not regulated
(essential for survival so are expressed all the time)Some produced at certain times, in certain amountsDifferent causes:Variation in environmental conditionsCellular differentiation
Gene Expression
Understanding:Gene expression is regulated by proteins that bind to specific base sequences in DNA Slide5
Different proteins used to regulate transcription
Different sections of DNA bases where these proteins bindUnique to the specific gene they are regulatingEnhancersSilencersPromoter-proximal elements
Gene Expression
Understanding:Gene expression is regulated by proteins that bind to specific base sequences in DNA Slide6
Promoters
Enhancers
Promoter-proximal elements
SilencersSlide7
Promoter proximal elements
Understanding:
Gene expression is regulated by proteins that bind to specific base sequences in DNA
Near to promoterSpecific sequence for each geneContains other regulatory elementsSlide8
Increase the rate of transcription
Does not need to be near promoter
Decrease the rate of transcription Does not need to be near promoter
EnhancersSilencers
Understanding:
Gene expression is regulated by proteins that bind to specific base sequences in DNA Slide9
Applications:
The promoter as an example of non-coding DNA with a function
Located near a gene Binding site of RNA polymeraseInitiates transcriptionPromoters are not transcribed into RNASame sequence for most genes (general RNA polymerase binding)
PromotorsSlide10
Your characteristics are due to your environment, your genes, or a bit of both.
Put the characteristics on the scale
Nature vs NurtureUnderstanding:The environment of a cell and of an organism has an impact on gene expression
EnvironmentalInheritedEYE COLOUR
SCARS
TATTOOS
ACCENT
WEIGHT
HAIR COLOUR
INTELLIGENCE
SUN TANSlide11
Production of skin pigmentation during exposure to sunlight
Melanin produced to protect against UV rays from the sunGene regulation in response to environmentGene Regulation
Understanding:The environment of a cell and of an organism has an impact on gene expressionSlide12Slide13
Many studies on identical and non identical twins raised together or apart
More evidence for intelligence is inheritedMr. Burford: THE JIM TWINS Gene Expression
Understanding:The environment of a cell and of an organism has an impact on gene expressionSlide14
DNA molecules are paired with a protein called histone
Histones help to package DNA8 histones make up a nucleosomeEssential as DNA can be 4cm long, it must fit into a microscopic nucleus
Prior Learning
Understanding:Nucleosomes help to regulate transcription in eukaryotesSlide15
Chemical modification of histones is important in whether a gene is expressed or not.
Add:Acetyl group (COCH3)Methyl group (CH3)Phosphate group (PO4)Increase or decrease the accessibility of the gene to transcription factorsImpact the visible characteristics of an
individualEpigenetic tagsNucleosomes
Understanding:Nucleosomes help to regulate transcription in eukaryotesSlide16
Direct methylation of DNA decreases gene expression
Methylation of histones can increase or decrease gene expressionMethylation
Skills:Analysis of changes in DNA methylation patternsSlide17
Evidence that chemical modifications that occur to DNA in one generation may be passed onto the next
Sum of epigenetic tags in an organism = epigenomeEpigenetic Tags
Nature of science:Looking for patterns, trends and discrepancies: there is mounting evidence that the environment can trigger heritable changes in epigenetic factorsSlide18
Initiation (start at promoter)
Elongation (build)
Termination (RNA completed and breaks off at terminator)
5’3’
3’
5’
Transcription starts at
a
promoter
5’ to 3’ direction
Transcription
Understanding:
Transcription occurs in a 5’ to 3’ direction Slide19
RNA polymerase binds to
promoterDNA unwindsH bonds break Strands separateAdds the 5’ end of a free nucleotide to the 3’ end of the growing mRNA molecule
Understanding:
Transcription occurs in a 5’ to 3’ direction InitiationSlide20
Enhancers speed up rate of transcription
Silencers slow down rate of transcriptionFree RNA nucleotides attracted to complementary base pairs (AU, CG)Nucleotides joined by RNA polymerase in 5’ to 3’ direction
ElongationUnderstanding:Transcription occurs in a 5’ to 3’ direction Slide21
RNA
reaches terminator and detachesH bonds breakRNA molecule detaches from DNADNA forms double helix again (H bonds form)Many RNA polymerases can follow one anotherTermination
Understanding:Transcription occurs in a 5’ to 3’ direction Slide22
Termination
Intiation
ElongationSlide23
Prokaryotes: No
nuclear membrane: transcription and translation coupledEukaryotes: can carry out modification before mRNA leaves nucleusPost Transcriptional Modification
Understanding:Eukaryotic cells modify mRNA after transcription Slide24
Pre-mRNA
mature mRNA RNA splicing(Introns removed and exons joined together)Post Transcriptional Modification
Understanding:Eukaryotic cells modify mRNA after transcription Slide25
Allows one gene to code for multiple proteins
Must have multiple exonsExons may or may not be included in mRNAPost Transcriptional Modification
Understanding:Splicing of mRNA increases the number of different proteins an organism can produceSlide26
Explain the process of DNA transcription leading to the formation of mRNA
(8 marks)Exam QuestionSlide27
RNA
polymerase; (polymerase number is not required)binds to a promoter on the DNA;unwinding the DNA strands;binding nucleotides to the DNA;it moves along in a 5′→3′ direction;using complementary
pairing/Adenine-Uracil and Cytosine-Guanine;until a terminator signal is reached;RNA detaches from the template and DNA rewinds;RNA polymerase detaches from the DNA;many RNA polymerases can follow each other;introns have to be removed in eukaryotes to form mature mRNA; 8 maxMark Scheme