Topic 8 - Gene Expression Flashcards
What is a stem cell?
An undifferentiated cell which can keep dividing to give rise to other cell types
What is a totipotent stem cell?
It can form any type of cells, including embryonic cells
What is a pluripotent stem cell?
Form any cell type, just not embryonic cells
What is a multipotent stem cell?
Differentiate into other cell types but are more limited
What is a unipotent stem cell?
Only differentiates into one type of cell
How is an induced pluripotent stem cell made?
Created from unipotent stem cells
How does a transcription factor allow transcription to occur
Transcriptional factor moves from the cytoplasm to the nucleus
It binds via the DNA binding site to a specific base sequence in the promoter region of a gene
This stimulates RNA polymerase and therefore causes transcription
mRNA is produced
What is the role of oestrogen before transcription can occur
Oestrogen diffuses across the the membrane - it is lipid soluble
It binds to the receptor
Transcriptional factor changes shape
Binds with DNA - transcription occurs
What is meant by epigenetics?
A heritable change in gene function without change to the base sequence of DNA
How does increased methylation of DNA affect gene transcription
Addition of a CH3 group to cytosine bases
Acetylation is decreased
The DNA-histone complex is more condensed
This creates heterochromatin
Prevents the transcription factors from binding and therefore no gene is expressed
How does decreased acetylation of DNA affect gene transcription
Positively charged histones bind to negatively charged DNA
Decreasing acylation increases positive charge of histones
Binding becomes too tight and this prevents the transcription factors from binding to the promoter region
What is DNA methylation and DNA acetylation
Methylation = methyl groups added to the cytosine of DNA
Acetylation = decreased acylation of histones increases their positive change, they bind to DNA tighter
How does epigenetic changes affect humans
Can cause disease, for example cancer
Either by over activating a gene’s function or by suppressing it
Application of epigenetics
Treatment of various diseases - drugs can be used to stop enzymes and proteins that change methylation and acetylation levels
Process of RNA interference
siRNA (small interfering RNA) binds to a complementary sequence of mRNA.
mRNA is broken down by enzymes and therefore no translation can occur.
