3.8 Regulation of transcription and translation, gene expression and cancer Flashcards
When does transcripition of a gene occur ?
When a molecule from the cytoplasm enters the nucleus and binds to DNA in the nucleus
What is a transcription factor ?
Proteins that can bind to different base sequences of genes and initiate transcription of genes
What is oestrogen ?
A steroid hormone that can initiate transcription
What happens when oestrogen binds to a TF ?
It causes the DNA binding site to change shape slightly and this makes it complementary and able to bind to the DNA and initiate transcription
What is epigenetics ?
The heritable changes in gene function without changing the DNA base sequence
What effect does increased methylation have on transcription ?
Increased methylation of DNA inhibits transcription
Why does increased methylation inhibit transcription ?
As when methyl groups are added to DNA they attach to the base cytosine, this prevents TFs from binding and attracts proteins that condense the DNA-histone complex
What affect does decreased acetylation have on transcription ?
Decreased acetylation inhibits transcription
Why does decreased acetylation inhibit transcription ?
As if acetyl groups are removed from the DNA the histones become more positive and are attracted more to the phosphate group on DNA. This makes the DNA and histone more strongly associated and hard for the TFs to bind
What is RNAi (RNA interference) ?
When a mRNA molecule that has already been transcribed gets destroyed before it is translated to create a polypeptide chain
What are the properties of benign tumours ?
- Non-cancerous
- Grow very large but at a slow rate
- Often surrounded by a capsule so remain compact and can be removed by surgery
- Impact is localised
What are the properties of malignant tumours ?
- Cancerous
- Grow rapidly
- Does not produce adhesive so can metastasise (spread to other parts of body)
What is a proto-oncogene ?
Proteins involved with the initiation of DNA replication
What are oncogenes and what effect do they have ?
They are mutated versions of a porto-oncogene and can result in DNA replication becoming permanently activated and mean cells divide continuously
What are tumour suppressor genes ?
They produce proteins to slow down cell division and to cause cell death if DNA copying errors are detected
