21. Gene expression

• How is transcription stimulated

  Transcriptional factors move to the nucleus and bind to the promoter region of DNA. This allows RNA polymerase to bind and transcription is stimulated
• How does oestrogen stimulate transcription

  Binds to transcriptional factors which changes the shape. Causes the inhibitor molecule to be released and so can then bind to DNA
• How does interference RNA regulate translation

  Double stranded RNAi becomes singular stranded and associated with nuclease enzyme. This binds to a specific mRNA molecule and cuts it in two so synthesis stops
• What is a use of interference RNA in scientific research

  Maybe possible to stop a faulty protein from being produced and prevent a condition which is caused by faulty jeans
• Why are all cells in an organism genetically identical?

  Mitosis
• What are the two features of stem cells?

  They are undifferentiated, but can differentiate into cells

  They can replace themselves
• What are the four types of stem cell?

  totipotent

  Pluripotent

  multipotent

  unipotent
• What are totipotent cells 


  Found in embryos

  can produce any type of cell
• What are pluripotent cells 


  Found in embryos

  can become any type of cell apart from placenta cells
• What are multipotent cells

  Found in tissues of mammals

  can become a limited number of cells
• What are unipotent cells

  Found in mature mammals

  can only become one type of cell
• What are induced pluripotent cells

  Pluripotent cells produced from adult body cells. Able to divide to produce new IPS cells
• What are uses of stem cells

  Used to replace damaged cells like leukemia or burns
• Ethical arguments for using stem cells

  • move towards reproductive cloning
  • an embryo is just a ball of cells
  • can prevent human suffering
• Ethical arguments against stem cells

  • embryos have potential for life
  • wrong to use things that can’t give consent
• What kind of stem cells do plants have

  Totipotent
• What is epigenetics 


  Heritable changes in gene function without changes to base sequence of DNA
• What is a histone

  Protein that DNA is wrapped around
• What is epigenome 


  All the chemical tags that have been added to a persons genome
• What are the chemical tags on DNA

  Acetyl group or methyl group
• What is acytylation of histones

  The acetyl group binds to the histone proteins

  causes DNA to loosen around the histone

  makes the promoter region accessible

  transcriptional factors can bind and so gene is turned on
• Where do the acetyl groups bind

  Histone
• Where do methyl groups bind

  Cytosine
• What is methylation

  Opposite of acetylation
• What are benign tumours

  They don’t spread (not cancer)
• What are malignant tumours

  Spread (cancer)
• What two genes play a role in controlling rate of mitosis

  Proto oncogenes

  tumour suppressor genes
• What do proto oncogenes do

  Stimulate cell division
• What do tumour suppressor genes do

  Inhibit cell division