When things don’t go as planned. MUTATIONS & CANCER When things don’t go as planned.

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Chromosomal mutations involve segments of chromosomes, whole chromosomes, and even entire sets of chromosomes. Gene mutations involve individual genes.

Gene Mutation A gene mutation is a change in the order of the A, G, C, and T bases in a gene. Gene mutations can be positive negative neutral Mutagens are substances or factors that can cause mutations in DNA. One form of gene therapy is the replacement of a faulty gene with a healthy copy of the gene.

Types of Mutations A gene mutation results when the specific order of the A, G, C, and T bases that make up a particular gene changes. A mutation can occur any time in the life of a cell. Types of gene mutations include: deletion (one base is missing) addition (an extra base is added) substitution (one base is substituted for another) Chromosome mutation during meiosis

An Example: The White Kermode Bear In the case of the white kermode bear, there is a mutation in a single base in the gene for coat colour found in 1 out of every 10 black kermode bears. Both parents must have this altered gene in order to produce a white bear, and the bear must receive both copies of the gene.

Positive Mutations Errors in the sequence of DNA bases may produce proteins that could be beneficial to an organism and therefore to the survival of its species. Ex: A few individuals with Northern European /Central Asian descent carry a mutated gene that produces the instructions for a protein that prevents HIV from infecting the person by not allowing the HIV virus to bind and enter the cell. These individuals have been found to be resistant to the virus and, therefore, to AIDS.

Negative Mutations Small changes in the sequence of bases can also cause a harmful or negative mutation. The substitution of the base A for the base T in only one position on the gene causes the protein hemoglobin to take on a different shape. This differently shaped hemoglobin molecule causes sickle cell anemia.

Neutral Mutation The substitution of one base for another in the DNA sequence of a gene may not change an organism. The same protein will be made and may still function normally. The change caused by the mutation does not increase or decrease the survival rate of the organism. The white coat colour of the Spirit Bear is considered to be a neutral mutation.

Chromosome Mutation Big changes in the organization of DNA and genes happen when pieces of chromosomes are lost, duplicated, or moved within a chromosome or moved to another chromosome. These changes often occur during meiosis. They affect many genes in the chromosome and change the proteins made by those genes.

Types of chromosome mutation

Genetic Disorder Understanding which chromosomes have been affected helps physicians diagnose and treat patients with genetic disorders or syndromes. One example is Down syndrome, which is one of the most frequently occurring types of chromosome mutations. Ninety-five percent of the cases of Down syndrome are caused by an extra 21st chromosome.

Mutagens Mutagens are substances or factors that can cause mutations in DNA. Cigarette smoke, radiation from X rays or UV rays, pollutants such as mercury, and even household chemicals are examples of environmental mutagens that can cause mutations. When DNA becomes damaged, the proteins in a cell will not be made correctly.

Cell Check Points Activities within the cell during the cell cycle are monitored and controlled at specific stages, or checkpoints. Special proteins at these checkpoints monitor cell activities and send this information to the nucleus. The nucleus then instructs the cell whether or not to divide. Cells will not divide if: There are not enough nutrients to support cell growth. DNA within the nucleus has not been replicated. DNA is damaged.

The Cell Cycle and Cancer If a mutation occurs in a gene producing the instructions for a checkpoint protein, cell cycle control will be lost. As a result, a damaged cell may divide uncontrollably. Cancer is the name given to certain diseases that result from uncontrolled cell division.

How Cancer Grows Normal cells grow in a single layer and stop dividing when they receive messages from neighbouring cells. Cancer cells do not respond to messages from nearby cells, so they begin to grow in multiple layers. These multiple layers form a tumour.

How a Tumour Grows

Cancer Cells Cancer cells are not specialized, so they do not function as part of your body. Cancer cells release chemicals to attract small nearby blood vessels. The blood vessels branch into the tumour and deliver nutrients to it. Cancer can spread to other areas of the body if some tumour cells break away and are carried by the blood vessels to a new location where they may begin to divide and form a new tumour.

How Cancer Spreads or Metastasizes. What does cancer look like?                                                                                                                          How Cancer Spreads or Metastasizes. Show Real Player Media File – Mayo Clinic – How melanoma spreads to the lungs. Nova: Cancer Warrior - How cancer spreads clip

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