Stem Cells & Control Of Gene Expression Flashcards
(38 cards)
How can cells from the same stem cell become different types?
Not all genes are switched on or off in each cell.
What controls which genes are switched on or off?
Promoters and transcription factors.
What are totipotent cells?
Cells that can give rise to a complete human or all cell types.
What are pluripotent cells?
Cells that can give rise to some, but not all, cell types.
Define epigenetics.
Heritable phenotype changes that do not involve changes to the DNA sequence.
Name a mutagenic agent.
High-energy radiation (e.g. alpha, beta, gamma, or X-rays).
Name another mutagen.
UV light.
Give one more example of a mutagen.
Carcinogens (e.g. benzene, mustard gas, phenols, tar).
What happens in a deletion mutation?
One or more bases are removed from DNA.
How does deletion affect the gene’s structure?
Causes a frameshift, changing the base sequence from the mutation point onward.
How can altered DNA lead to cancer?
Mutation changes the base sequence of a gene.
Which genes, when mutated, can lead to cancer?
Genes controlling cell growth, e.g. tumour suppressor genes or oncogenes.
How does a mutation affect tumour suppressor gene function?
It may change the protein’s structure, making it non-functional or preventing its production.
What does this loss of function cause?
Uncontrolled or rapid cell division, potentially leading to malignant tumours.
What is a malignant tumour?
A mass of undifferentiated cells undergoing uncontrolled division.
What key feature defines a malignant tumour?
The ability to spread (metastasis) and form tumours elsewhere in the body.
Why are fragments of cancer cell DNA found in blood plasma?
Cancer cells die and break open, releasing DNA.
How can methylation of tumour suppressor genes cause cancer?
Methylation prevents gene transcription.
What is the consequence of suppressed gene transcription?
No protein is made to prevent cell division or cause apoptosis, allowing mitosis to go unchecked.
What changes to tumour suppressor genes can lead to tumours?
Increased methylation or mutations.
What does this prevent?
The gene being transcribed or expressed.
How does this result in cancer?
Rapid, uncontrolled cell division.
How does a signal protein cause mRNA synthesis?
Binds to a membrane receptor.
What happens after receptor binding?
A messenger molecule enters the nucleus.
