Cell dev lc 1

  • Created by: Amh
  • Created on: 17-03-16 20:05
How are the different cell types established during development?
'The genotype contains a developmental programme that unfolds and results in the expression of different sets of genes in different cell types.’
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What do factors that control gene expression regulate?
Chromatin structure, initiation of transcription,RNA processing, initiation of translation, post-stranslational modifications
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How does regulation of chromatin structure effect gene expresseion
DNA is associated with histones, the more tighly associated DNA is not avialable for transcription or for modifications
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What sort of modifications influence chromatin structure and gene expression
acetylation, methylation, phophorylation
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How does an acetylation modify DNA
Acetyl group binds to histone tails, promoting a loose chromatin structure that permits transcription
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How does DNA methylation effect gene expression
The addition of methyl groups ro certain bases in DNA is associated with gene silencing that can be past on
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What is genomic imprinting
a proces by which epigenetic modifications regulate expression of either maternal or paternal alleles of certain genes at the strt of development
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What is epigenetic inheritance
Epigenetic modifications can be passed on to emerging cells during development the epigenetic tags should be removed, but if they're not this is epigenetic inheritance
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Give an example of plant epigenetic inheritance
radishes are attacked by catapilallars and they produce nasty chemicals and spikes to stop the catapillars, the offspring of these radishes tdevelop these characteristics without the selective pressure
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How do water fleas provide evidence for epigenetic inheritance
waterfleas develop helemts in response to preditors, and is maintained by offspring without preditors for many generations
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Give an example of epigenetic inheritance in mammals
If you give preggo rats vinclozolin, the pups have life long shanges like low sprem count this is maintained by many generations.
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In what ways does regulation of transcription initiation factors affect gene transcription
via transcription factors, and signalling conductance pathways.
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In what way does regulation by transcription factors affect genes
Chromatin-modifying enzymes provide initial control of gene expression by making a region of DNA either more or less able to bind the transcription machinery. Transcription factors then control levels of transcription
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What is a gene
it is a section of DNA hat contains the inforamtion required for the production of biologicallly active RNA molecules
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What are control elements
Segments of non-coding DNA that help regulate transcription by binding specific transcription factors
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Why are control elements and transcription factors important
Critical to the precise regulation of gene expression in different cell types
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Why are transcription factors important
RNA polymerase require transcription factors to start transcription, essential for all protein coding genes, In eukaryotes, high levels of transcription of particular genes depend on control elements interacting with specific transcription factors
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why is the relationship between transcription factors and control elements important
A given gene may have many different control elements (enhancers). Expression depends on the complement of activator or inhibitor transcription factors present in the cell that can bind to these control elements.
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What is the TATA box
A promotor sequence of DNA that indicates where to begin transcription, it decides the direction and strand of transcription, trans factors bind to tata and recruit polymerase
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What protein is necessary for efficient RNA synthesis
TATA binding protein
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What is the BASAL transcription factor
just general transcription factors required for RNA polymerase II to bind to promoter regions and initiate transcription.
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What do cell specifc transcription factors do
iincrease or decrease complex stability thus increasing or decreasing gene expression
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Which can be coordinately controlled prokaryotes or eukaryotes
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How can eukaryotic genes be coordinately controlled
The coactivation of related genes can occur because they share a specific combination of control elements.
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Why is post transcriptional modification important
allows a cell to fine-tune gene expression rapidly in response to environmental changes
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What are some types/sites of post transcriptional regulation
RNA processing (alternative RNA splicing) mRNA degredation,
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How can RNA processsing affect gene expression
Alternative RNA splicing - different mRNA molecules are produced from the same transcript depending on which RNA segments are included
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How does mRNA degradation affect gene expression
Lifespan of mRNA incytoplasm regualtes protein synthesis. Life span is determined partially by squences in leader and trailer regions
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How does initiation of translation affect gene expression
Initiation can be blocked by regulatory proteins that bind to sequences or structures of the mRNA.
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Give an example where translation of all mRNAs in a cell may be regulated simultaneously
translation initiation factors are simultaneously activated in an egg following fertilization
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Why are non0coding RNAs important
regulate gene expression at two levels: mRNA translation and chromatin configurationregulate gene expression at two levels: mRNA translation and chromatin configuration
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What are MicroRNAs
small (22nt) single stands of RNA which bind to complementary sequences in the 3'UTR of target mRNAs - this blocks the mRNAs translation
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What is the 3'UTR
UTR- untranslated region (in this case on the 3' end) the section of messenger RNA (mRNA) that immediately follows the translation termination codon.
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What is RNA interference (RNAi)
The phenomenon of inhibition of gene expression by RNA molecules
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What does RNAi involve?
microRNAS, and small interfacing RNAs
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How do siRNAs and miRNAs differ
form from different RNA precursorsm and siRNA can be derived from external sources
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What is the basic mechanism behind RNAi
dsRNA is broken down by dicer and drosher in to siRNAs which have symmetric 2–3nt 3' overhangs and 5'-phosphate and 3'-hydroxyl groups, which when loaded to RISC can trigger the degradation of mRNA matching its sequence - silencing gene
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What is the RISC complex
RNA-induced silencing complex it is a ribonucleoprotein which has one siRNA/miRNA strand that acts as a template, complementary mRNA is found and Argonaute cleaves it
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How do siRNAa effect heterochromatin
it has a role in chromatin formation, and can block large ergions of the chromosome
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How can protein processing affect gene expression
after translation occur the protein is processed, if protein is ubiquitinated (a p.trans.mod) the protein will be detroyed
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Card 2


What do factors that control gene expression regulate?


Chromatin structure, initiation of transcription,RNA processing, initiation of translation, post-stranslational modifications

Card 3


How does regulation of chromatin structure effect gene expresseion


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Card 4


What sort of modifications influence chromatin structure and gene expression


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Card 5


How does an acetylation modify DNA


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