Regulation of Transcription and translation

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  • Created by: Hindleyc
  • Created on: 12-04-19 16:16
In eukaryotes what can transcription of target genes be
stimulated or inhibited when specific transcription factors move from the cytoplasm into the nucleus eg steroid hormone oestrogen initiating transcription
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How does it work
Controlling expression of a gene by controlling transcription
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what are there
100s of know TF each recognising and binding to a specific DNA sequence
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What are the TF regulated by
signals from other molecules eg horomones - steroid hormone controls protein synthesis via TF
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For transcription to being what happens to the gene
it is switched on by a specific molecule that move from the cytoplasm into the nucleus (these molecules called TF)
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What are they
molecules which can bind to the DNA and thus initiate transcription
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What are they most of the time
inactive in the cytoplasm because they have an inhibitor attached to them therefore no TF=no transcription as RNA polymerase cannot bind effectively
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SO what does it do
Regulate production of a protein from a gene
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What does each TF have
A site that binds to a specific base sequence of the DNA in the nucleus
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What happens when it binds
it causes this region of DNA to begin the the process of transcription (stimulates)
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What is produced
messenger RNA and the information it carries is then translated into a polypeptide
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When a gene is not being expressed (ie switched off) what has happened
the site on the TF that binds to DNA is not active
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Why
blocked by an inhibitor molecule
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As the site on the TF binding to DNA is inactive what can't it cause
transcription and polypeptide synthesis (translation)
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What do TF do
Activates ability of RNA polymerase
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What is transcription the most important
control- earliest and most effective point so mRNA not made if it is not needed
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For transcription to occur what must happen
RNA polymerase must bind to the DNA molecule upstream of the gene - promotor region (DNA binding protein)
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What does RNA polymerase do
binds only weakly and needs TF before can start transcribing gene
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What does TF also
bind to promotor region upstream of DNA polymerase
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how
dna flexibel loop to allow all different TF to bind which activates RNA polymerase which can now move along the DNA molecule transcribing the gene
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what happens the the promotor region
TF binds allowing RNA polymerase to bind effectively allowing gene to be transcribed
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why
rna transcribed DNA but needs tf and if inhibited gene not expressed
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steroid vs protein hormone
S lipid soluble easily enter cells- diffuse easily across csm
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What is Oestrogen
secreted by ovaries and stimulates synthesis of many proteins in target tissues such as hypothalamus and breasts
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what can hormones like oestrogen do
switch on a gene thus start (stimulate) transcription of particular genes by combining with a receptor site on the TF
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What does this do
Activates the DNA binding site by causing it to change shape
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Steps
1-O is a lipid soluble molecule and therefore diffuses easily through the phospholipid portion of cell surface membranes 2, once inside cytoplasm of a cell O binds with a site on receptor molecule of TF as shape of site and O complementary
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By binding with site what happens
O changes shape of DNA binding site on the TF which can now bind to DNA (it is activated) and the TF can now enter nucleus through a pore and bind to specific base sequence on DNA
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What does the combination of the TF with DNA stimulate
transcription of the gene that makes up the portion of DNA
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O binds with receptor site on tf causing it to
release inhibitor change shape allowing to transcribe
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What RNA polymerase do
binds to promotor region to make RNA
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What ia controlled
which gene is translated from DNA to mRNA
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If gene not expressed
protein won't be present in proteome of the cell
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What is Epigenetic
involves heritable changes in gene function without changes to the base sequence of DNA
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What are these changes caused by
changes in environment that inhibit transcription
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how
increased methylation of DNA, decreased acetylation of associated histones
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What is epigenetics the study of
impact of environmental factors eg diet stress toxins etc on genetic inheritance
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why
can subtly alter the genetic inheritance of an organism offspring
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epigenome=
layer of chemical tags associated with DNA and the histone it is wrapped around
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What is DNA wrapped around
proteins called histones
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And what are both DNA and histones covered in
Chemicals (tags) and these form 2nd layer called epigenome
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what does epigenome determine
shape of DNA histone complex
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how
keeps genes that are inactive in a tightly packed arrangement therefore ensures they cannot be read (keeps switched off) called epigenetic silencing
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What does it do by contrast
unwraps active genes so that the DNA is exposed and can be easily transcribed (switch them on)
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What is the DNA code compared to E
fixed but epigenome is flexible because chemical tags respond to environemental changes
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What do factors like diet and stress casue
chemical tags to adjust the wrapping and unwrapping of the DNA and so switch genes on and off
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What can environmental influences such as diet and stress and toxins etc can affect
highness of the coiling of DNA around the histones and therefore degree of expression of the genes
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What can these acquired changes be
passed on to offspring
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What is the epigneome of the cell
accumulation of the signals it has received during its lifetime and it therefore acts like a cellular memory
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In early development what do signals from within the cells of the foetus and the nutrition provided by mother important in
Shaping epigenome at this stage
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After birth and throughout life what affects epigenome
Environmental factors although signals from within the body eg hormones also influence it
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What can these factors do
cause epigenome to activate or inhibit specific sets of genes
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what do Environmental signals stimulate
proteins to carry its message inside cell from where it is passed by series of other proteins into nucleus
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What happens here
message passes to a specific protein which can be attached to a specific sequence of bases of the DNA and once attached the protein has 2 possible effects
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2 possible effects
Can change acetylation of histones leading to activation of inhibiton of a gene or methylation of DNA by attracting enzymes that can add or remove methyl groups
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Card 5

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For transcription to being what happens to the gene

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