15 Control of gene expression Flashcards
Each transcriptional factor has a site that…
binds to a specific region of the DNA in the nucleus
For transcription to begin, the gene must be stimulated by…
transcriptional factors moving from the cytoplasm into the nucleus
The binding of a transcriptional factor to DNA
stimulates the region to begin transcription
When the transcriptional factor is blocked by an inhibitor molecule,
a gene is not being expressed
Hormones can switch on genes by…
combining with transcriptional factors in the cytoplasm and moving into the nucleus
siRNA is…
small, double-stranded sections of RNA
siRNA is produced from
large, double-stranded molecules of RNA being cut into smaller sections by enzyme, ‘dicer’
siRNA molecules combine with…
and enzyme to form a RISC complex
the RISC complex…
binds to specific, complementary mRNA molecule
the RISC complex, once in position, breaks … into smaller sections with the enzyme …
the RISC complex, once in position, breaks mRNA into smaller sections with the enzyme slicer
Once mRNA has been acted upon by slicer,
the mRNA can no longer be translated
Potential uses for siRNA
identification of genes in pathways,
blocking of detrimental genes in pathways
Cells in which no genes have been switched off are called…
TOTIPOTENT (not specialised)
All cells contain the…
same genes
Although all cells contain all genes,
only certain genes are expressed in any one cell at any one time
Differentiated cells produce…
different proteins
Totipotent cells…
Can mature into any body cell
Two ways gene expression can be controlled:
- prevent transcription, therefore mRNA production
- break down mRNA before the code can be translated
Totipotent cells in mature animals are named…
adult stem cells
Stem cells are…
undifferentiated dividing cells that occur in adult animal tissues and must be constantly replaced
Embryonic stem cells occure…
at the earliest stage of embryo development, before cells have differentiated
If a plant is genetically identical to the one from which a root cell it was grown from, it is
a clone
