Properties of Stem cells
- Will keep replicating, hence replacing themselves;
- Undifferentiated so can differentiate into other cells (totipotent)
How can injecting stem cells to patients with heart disease help improve muscle contraction
- stem cells would develop into heart muscle cells;
- the relevant genes would be expressed
Explain how unspecialised cells can develop into different types of tissue
- cells are totipotent meaning they can develop into any cell type
- different genes expressed
- so different enzymes and proteins produced
Why should a person's stem cells be used in an experiment
- Own stem cells used to minimise risk of rejection
- Totipotent so can divide into 'required cells' and fight appropriate issue
Describe the role of oestrogen in protein synthesis
- Oestrogen is a lipid, so crosses the cell membrane by lipid diffusion and enters the cytoplasm.
- Oestrogen binds to its receptor protein in the cytoplasm to form a hormone-receptor complex. Receptors changes shape and the inhibitor molecules is released, exposing the binding site
- This complex is now a transcription factor.
- The activated transcription factor diffuses into the nucleus through a nuclear pore.
- Complex can act as an activator or repressor so it can inhibit RNA P or facilliate it
- In the nucleus the transcription factor binds to the DNA promoter,
- This binding stimulates RNA polymerase to transcribe genes and so stimulates protein synthesis.
Structure of siRNA
small as it consists of only 20–25 nucleotides;
- double-stranded RNA
How does siRNA interfere with gene expression
- single siRNA strand;
- binds to mRNA;
- by complementary pairing;
- enzyme cuts up mRNA
- this prevents translation
How can addition/ deletion of DNA cause cancer?
- Inactivates tumour suppressor gene;
- Unable to control cell division
- Rate of cell division increased
Role of transcriptional factors in making proteins
- Binds to DNA at specific region (promoter );
- Activates RNA polymerase
- Stimulate transcription
- It can turn on gene
How can siRNA be used in treating diseases?
- Some diseases are genetic
- siRNA will stop non-functional protein of this gene being made
Why doesn't siRNA only affect the expression of other genes
- base sequence of siRNA complementary to one mRNA;
- will only bind to and destroy this mRNA
What is a transcriptional factor