Gene Expression Flashcards
(46 cards)
What are the three kinds of change to the base sequence that cause a mutation?
Insertion, Deletion and Substitution
What is base substitution?
A mutation which switches out a single base for another which alters a single amino acid, not the whole protein May not even have an effect if the substituted base is the third in a codon
What is an insertion?
Where a base is inserted, causing a reading frame shift, affecting the rest of the protein
What is a deletion?
Where an original base is removed, causing a reading frame shift affecting the rest of the protein
What are the three kinds of mutation?
Non-sense, mis-sense and silent
What is a silent mutation?
A mutation which results in no change to the amino acid sequence
What is a non-sense mutation?
A mutation which results in the formation of a stop codon
What is a mis-sense mutation?
A mutation which changes the amino acid(s) being coded for potentially resulting in a non-functional protein or not being made at all
What causes mutations?
Exposure to mutagens
What are mutagens?
Ionising radiation or certain chemicals like carcinogens
What is a malignant tumour?
- More mutations than Benign
- Can invade other tissues so it is hard to determine boundary of tumour
- Fast Growing, Cells recruit formation of blood vessels
- Can invade other tissues by metastasis
- Cancer Forming
What is a benign tumour?
- mutations in one or two controlling cells
- localised populations of cells, distinct demarcation
- Growth rate matches death rate
- Cannot invade other tissues
- Non-cancerous
What two genes cause cancer if mutated?
- Proto-oncogenes
- Tumour suppressing genes
How does a mutation in a proto-oncogene cause cancer?
Proto-oncogenes encode proteins which stimulate cell division when activated. If it is mutated the gene becomes an ‘oncogene’ which makes too much permanently activated protein so cell division occurs constantly which can cause cancer
How does a mutation in a tumour suppressing gene cause cancer?
Tumour suppressing genes encode proteins which inhibit cell division when activated. when the gene is mutated the protein is not synthesised so cell devision is unchecked.
Is the mutation that turns a proto-oncogene into an oncogene dominant or recessive?
Dominant
Is the cancer causing mutation of the tumour suppressing gene dominant or recessive?
Recessive.
What are the 5 points at which gene expression can be controlled?
- Transcription
- Post transcriptional modification
- Longevity of mRNA
- Translation
- Post translational modification
How is gene expression controlled during DNA Transcription?
Transcription factors determine which genes are expressed
How is gene expression controlled during Post-transcriptional modification?
different Splicing means different mRNA so different proteins coded for
How is gene expression controlled by the longevity of mRNA?
If mRNA does not last very long, less of it can be translated into proteins. The longer it lasts the more protein will be made from it
How is gene expression controlled during DNA Translation?
Ribosomes control how much protein is translated
How is gene expression controlled during post translational modification?
The activity of the protein can be altered by other enzymes
How do transcription factors control DNA Transcription?
Transcription Factors bind to the promoter region to influence the binding of the RNA Polymerase enzyme. Some Transcription Factors activate transcription from here while others inhibit it.
