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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

  1. Oestrogen is a lipid, so crosses the cell membrane by lipid diffusion and enters the cytoplasm.
  2. 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
  3. This complex is now a transcription factor.
  4. The activated transcription factor diffuses into the nucleus through a nuclear pore.
  5. Complex can act as an activator or repressor so it can inhibit RNA P or facilliate it
  6. In the nucleus the transcription factor binds to the DNA promoter
  7. 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

  • A Protein that moves from cytoplasm to nucleus;
  • TF  binds to promoter
  • They can allow/prevent RNA polymerase to bind to DNA;
  • Leads to/prevents pre mRNA production