Chapter 20

• What is a gene mutation?


  a change in sequence of the bases in DNA
• What are the 2 ways mutation can occur?

  Spontaneously or through exposure
• What is a substitution mutation?


  one nucleotide is replaced by another in the DNA sequence.
• What is a deletion mutation?


  A nucleotide is lost from the normal sequence
• What is an addition mutation?

  A nucleotide is gained to the normal sequence
• What is a duplication mutation?

  the duplication of a segment of DNA.
• What is an inversion mutation?

  A mutation that involves the reversal of a segment of DNA
• What is a translocation mutation?


  Group of bases from one chromosome goes to another, leading to an abnormal phenotype
• What is a frame shift?


  A mutation that shifts the reading frame of a gene, resulting in a different amino acid sequence.
• What is a missense mutation?


  Changes amino acid
• What is a silent mutation?


  No change to the protein
• What is a nonsense mutation?

  Could generate a stop codon, leading to an incomplete amino acid
• What is a Tumour?


  Abnormal group of dividing cells
• What is a benign tumour?


  Non-cancerous growth.
• What is a malignant tumour?


  A cancerous growth that can invade nearby tissues and spread to other parts of the body.
• What is a proto-oncogene?

  stimulate cell division by producing proteins to make cells divide
• What is a tumour-supressor gene?

  Inhibit cell division by producing a protein that stops division or causes cell-death
• What can a proto-oncogene mutate into?

  An oncogene
• What does an oncogene do?

  permanently activates the growth factor, causing cells to divide uncontrollably
• What happens if a tumour suppressor gene is made inactive?

  Nothing inhibits cell division as protein is not produced. Cells divide uncontrollably
• What is methylation?

  Addition of a methyl group to a molecule.
• What does the hypermethylation of a tumour suppressor gene cause?


  Occurs in the promoter region of a tumour suppressor gene and causes the methyl groups to wrap tightly around the histones. Transcriptional factors cannot bind and so transcription is inhibited. Tumour suppressor gene made inactive
• What does the hypomethylation proto-oncogene gene cause?


  Causes them to act as oncogenes, increases production of proteins that encourage cell division, and leads to tumours.
• How can oestrogen trigger a tumour?


  As more cells are dividing, the chance of mutations occurring increases. This increases the chance of natural cancer.
• What are the differences between tumour cells and normal cells?


  Irregular shape, darker and larger, don't produce all necessary proteins, different antigens on their surface, don't respond to growth regulating proccesses
• What are the 4 sources of stem cells?

  embryonic, umbilical, placental, adult
• What are stem cells?

  undifferentiated cells that have the ability to develop into different types of specialized cells in the body.
• What are the 4 types of stem cells?

  Totipotent, pluripotent, multipotent, unipotent
• What is a totipotent stem cells?


  From an embryo and are capable of differentiating into any type of cell
• What is a pluripotent stem cell?


  From an embryo, can differentiate into almost any type of cell.
• What is a multipotent stem cell?

  From adult and umbilical cord stem cells, can differentiate into a particular group of cells.
• What is a unipotent stem cell?


  Comes from multipotent stem cells, can differentiate into a single cell type
• What are induced pluripotent stem cells?


  Induced pluripotent stem cells are adult cells that have been reprogrammed to have the ability to differentiate into any type of cell in the body.
• Why were IPS's created?


  Embryonic cells, while having the greatest differentiation possibilities, come with some huge ethical concerns
• What are the potential issues that Induced pluripotent stem cells could fix?


  Paralysis due to nerve damage.

  Insulin production in B-cells

  Skin cells and burns

  Leukaemia, cancer in blood cells
• What are the steps for culturing embryonic stem cells?

  1. Culture the early embryo in vitro.
  2. Treat with an appropriate 'differentiation factor'
  3. Cells will then differentiate into desired tissue.
  4. Used to treat diseases
• What stem cells do plant cells have?

  mature plants have many totipotent cells
• How are plant stem cells used?


  Exploited commercially for many years through tissue culture
• What is an example of plant stem cells being used in tissue culture?


  Cells from the root of a carrot can be grown into new carrots, in a medium with the correct growth factors to stimulate growth and differentiation
• What are the two ways cells control gene expression?


  Regulation of transcription.

  Regulation of translation