Theme 2-CB 15 Flashcards
What 2 effects can transient signals have +e.g.s:
1) temporary changes in gene expression e.g. nutrition, inflammation
2) permanent changes in gene expression e.g. development
Why is transcription regulation important?
allows cells to be specialised and stay specialised as allows cells to differentially regulate genes in the genome. this also means it can changing levels of protein synthesis in response to signals
What are the key stages of development
gametogenesis, fertilization, embryonic development, birth, adult development, reproduction
Gene expression has to be…
right time right place right cell type (tisse and organs can be a mix of cells) in response to the right conditions in the right amount
There are a limited number of TF, so how is a specific gene regulated?
- inidivdula factors can act on more than one gene
- factors work in different combinations
What are the 2 types of factors?
activator
repressor
Why is combinatorial control of gene expression important?
It means a group of genes can all be switched on and off at the same time, as each TF must be present for gene to be expressed for example in hepatic cells many genes are translated in response to a single hormone activating a TF= amino acids being made into glucose as a result of extreme exercise or starvation`
What transcription factor causes a fibroblast to specialise into a muscle cell?
what evidence is there off this?
MyoD
fibroblasts from skin of chicken embryo are converted into muscles cells and fuse by induced expression of MyoD gene.
Why is it important that Combination control exsists?
it means there can be lost of different cell types
How does a single TF lead to cell differentiation? e.g. fibroblast to muscle cell
TFs can act on genes for other TF and other signalling molecules (like Sonic Hedgehog)
depending on the combo of TF it drives cell along specific differentiation paths
1) What are homeotic genes?
2) What are homeobox genes?
3) What are Hox genes?
i. e. what info do they give? what do they encode for? What do they do?
4) What is the significance of Hox genes?
1) in control of morphogenesis
2) Contains a DNA sequence that encodes for an amino acid sequence called homeodoman sequence which can bind to enhancer regions, all homeobox genes are homeotic genes, some homeobox genes are not Hox genes, encode TF
3) Supply positional info. to the cell and encode for TF, They activated cascades of other regulators (TF and signalling molecules) and initiate feedback loops.
4) evolutionarily conserved
What are the effects of a Hox mutation?
abnormalities of limb development e.g. synpolydactyl
What are the effects of a Pax mutation?
development disorders of the teeth, eye, kidney and skin e.g. Waardenburg’s syndrome and hypodontia
WHat are the effects of Msx gene?
Craniofacial and dental disorders e.g. craniosynostosis syndromes and hypodontia
What molecules are important in developmental regulation?
1) TF (e.g. products of Msx, Pax and Hox genes)
2) Extracellular signalling molecules (e.g. morphogens (e.g. SHH)& Growth factors (Bone morphogenetic protein &TBF beta)
3) Receptors for signalling molecules ( e.g. fibroblast growth factor receptor)
4) Post-transcriptional control e.g. microRNAs
