Page 54 - Cell biology PDG 2024
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Promotor: are DNA sequences that can tell where transcription of a gene
begins. It is located upstream the transcription initiation site (at the 5'
end)
Activators: they are proteins that enhance the interaction between RNA
polymerase and a particular promoter thus encouraging gene expression
Enhancers: they are sites on the DNA that increases the transcription of
genes by binding to activators making the DNA loop to bring a specific
promoter to the initiation complex. Enhancers are found in eukaryotes
Silencers: they are regions on the DNA that can silence expression of the
gene when transcription factors bind to them
Transcription factors: they are proteins that can turn the gene expression
on and off by binding to either the enhancers or the silencers on the DNA
respectively thus regulating gene expression. Other transcription factors
bind to the promotor sequence on the DNA with the RNA polymerase
making transcription initiation complex that will initiate transcription
Proto-oncogene: it is a normal gene that could become an oncogene due
to mutations or increased expression
Oncogene: it is a gene that can cause cancer. Normal cells will undergo
apoptosis when important functions are altered. Activated oncogenes can
stop apoptosis making these cells survive and proliferate leading to tumor
formation.
Tumor suppressor gene: it is a gene that checks and regulates cell
division. When being mutated, it is unable to do its job leading to survival
and growth of the cell resulting in tumor formation
1) Regulation of Transcription
What are the factors that can switch transcription on or off?
Transcription is regulated by binding between transcription regulating
proteins and regulatory sequences on DNA.
We previously said that promoters indicate where transcription begins,
but the genes have additional regulatory sequences on the DNA that
control when a gene is transcribed. These regulatory sequences are
recognized and bound tightly by transcriptional regulators. The binding of
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