Unit 1: Genes and development Flashcards
How are genes differentially regulated (4) ?
1) Transcription factors
2) Epigenetic regulation
3) RNA stability and selective translation
4) Protein modification
What is a transcription factor (3) ?
- A protein that attaches to a specific part of DNA
- Regulates the transfer of information from DNA to RNA
- Necessary to turn on and off other genes during development
How do transcription factors activate or repress gene transcription ?
By binding to sites in promotor and enhancer regions
TFs are modular and combinatorial- what does this mean ?
They do not function by themselves (Rather as a group)
What are the 4 ways of finding TF binding sites ?
1) Promotor bashing
2) DNA binding assays ‘gel shift’
3) Chromatin immunoprecipitation
4) Genetics- analysis of mutations
What is promotor bashing ?
- It is a technique used to identify the regulatory elements within a gene’s promoter region
- By systematically mutating or deleting parts of the promoter
Explain the process of DNA binding assays “gel shift” (5)
1) Take piece of DNA that contains sequence
2) Radioactively label the DNA
3) Bind DNA to extract sequences that express TFs
4) Run on gel
5) Probe bound to DNA= bigger complex
What is chromatin immunoprecipitation (3) ?
1) Type of experiment that uses antibodies to recognise TFs
2) Can be used to extract TFs and see what DNA sequence bound to
3) Can be done in vivo or in vitro
What is epigenetic regulation ?
Heritable and reversible cellular and organismal traits that do not involve changes to the underlying DNA sequence
What are 3 exampled of epigenetic regulation ?
1) Chromatin
2) Histone modifications
3) DNA methylation
What is composed in a nucleosome ‘bead’ ?
- 8 histone molecules
- 146 base pairs of DNA
What is the difference between nucleosome and chromatin structure ?
1) A nucleosome is the basic structural unit of chromatin, consisting of DNA wrapped around histone proteins
2) Chromatin refers to the entire structure of DNA and proteins, including nucleosomes and their higher-order folding, and plays a key role in DNA packaging and regulation
How can histone tails be modified ?
- Methylation
- Acetylation
- Phosphorylation
What is a CpG site ?
A cytosine residue next to a guanine
How can DNA methylation lead to gene inactivation (2) ?
1) CpG sites within a promotor region can be methylated (add CH3 residue)
2) When enough cytosines are methylated this signals a cessation of gene transcription in target gene
What are 3 features of RNA regulation ?
1) RNA stability
2) Selected translation
3) RNA splicing
Why is RNA stability important for development (2) ?
1) As transcription is largely absent during early stages
2) Post transcriptional control is therefore a key means of regulating gene expression
Why is the transcription step skipped during early development ?
As early cell division is fast
What is differential splicing ?
Differential splicing (or alternative splicing) is a process where different mRNA isoforms are generated from a single pre-mRNA transcript by including or excluding specific exons or portions of exons and introns
What are microRNAs important for ?
They are an important mechanism of inhibiting translation
How are proteins phosphorylated ?
- Phosphates added by kinases
- Phosphates removed by phosphatases
What does the phosphorylation of IkB regulate ?
- NFkB Localisation
- Extracellular cue triggers signalling cascade
- Phosphorylation of IkB inhibits it (Degradation)
- NFkB enters nucleus, binds to DNA sequences on promotor and leads to transcriptional activity
What are Ike and NFkB ?
- IkB is an inhibitor of kB
- NFkB is a nuclear factor kappa B
