Introduction to the control of gene expression Flashcards
How are genes regulated in time
- During development
2. In response to hormones, infection and other signals
How are genes regulated in space
Different tissues or cell types express different genes
What happens when regulation fails
- Metabolic disease
- Metastasis
- Congenital disease
- Cancer
What happens when genes are over expressed
Drosophila homeotic mutants
- Bithorax
- Antennapedia
What is Beta-thalassaemia
Group of genetic disorders caused by insufficient expression of beta-globin
How is Beta-thalassaemia a mutation
- single base change in the TATA box therefore the gene cant be transcribed
- Single base change at the spilceosome signal sequence therefore it cant be recognised so the mRNA cannot be spliced
What does the 5’ UTR do in terms of translational control
It determines how efficiently the ribosome initiates translation
e.g. Globin is very efficiently translated whereas ferritin isn’t
How is the ferritin gene regulated
Its 5’ UTR has an Fe starvation inhibitor that requires an excess of Fe for the ribosome to be able to bind to the start codon
What does the 3’ UTR do in terms of translational control
It determines the stability of mRNA
e.g. Globin has a long stable mRNA but the immune stress hormone has a short unstable mRNA
What is miRNA, where does it come from and what does it do
Its a small non-coding RNA that controls post-transcriptional regulation. They are derived by processing from a larger precursor
RISC mRNA degradation process
A near perfect match of the guide and the target mRNA will cause the mRNA to be spliced and degraded
RISC mRNA reduced translation process
A partial match of the guide and the target mRNA will prevent the binding of the eukaryotic translation factor to the 5’ cap and also prevent the 60s ribosome subunit from binding to the target mRNA
