GN 301 Module 4: Effects of the Environment

Effects of the Environment

Rate of Spontaneous Mutation
  • 1 in 100,000 per gene per cell.   * We have 20,000 genes and trillions of cells   * 1/100,000 times, 20,000 genes → ==1 in 5 of our genes have some sort of mutation==

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Mutagen

Define Mutation:

  • Mutagen: an agent that raises the rate of mutation above the spontaneous rate

More than 1000 chemicals are listed as mutagens

  • Examples   * UV light, X rays, and chemicals, tobacco

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Ames Test:
  • What is mixed together?   * chemicals and bacteria are mixed together with liver enzymes
  • What is observed?   * the number of mutations that occur from the chemical
  • Why use liver enzymes/liver extract   * to mimic the human body’s enzymes to create a more realistic experiment
  • Interpret graph   * What is plotted on each axis   * Determine which chemical causes most mutations

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Effects of UV
  • Type of mutation caused is   * pyrimidine dimers
  • Xeroderma pigmentosum   * Causes: a defective DNA repair mechanism that repairs dimers   * Complications: tumors are created on skin area when exposed to UV light
Radiation
  • Avg person exposed to 6.2 mSV/yr (from all sources)

\ Nuclear incidents and their effects

  • How should you rank the following three episodes from most to least radiation released: Hiroshima, Fukushima, Chernobyl?   * Chernobyl released about 90 times as much radiation as the nuclear bomb in Hiroshima   * Chernobyl > Fukushima > Hiroshima nuclear bomb

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  • Interpret dose-response curve (Label axis, describe what is happening)

\  Graph showing the number of mutations (Y axis) v Radiation exposure (x axis). Line on graph shows linear increase of number of mutations as exposure increases and then a rapid curved drop off in mutations as damage gets so sever that a lethal does occurs.

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  • Radiation Exposure Values   * LD 50/60: Define and give numerical value and units

LD: lethal dose

  • LD 50/60 is the dose at which 50% of people exposed will die within 60 days of exposure

\ Safety standards - describe

  • In the workplace, it’s set so that the max dose a person can be exposed to is 20 mSv per year, with no more than 50 mSv in a year   * There are additional precautions for pregnant women   * Dose limit to Fukushima workers was 250 mSv

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  • Define and give examples   * Hereditary: traits transmissible from cell to cell or parent to child   * Congenital: traits that are present at birth, can be due to genes, environment or both   * Phenocopy: a condition resulting from environmental factors that mimics a genetic condition, such as vitamin D induced rickets or radiation induced microcephaly, when it’s not genetic at all   * Carcinogen: a physical or chemical agent that causes cancer (EX: Radiation, tobacco, some chemicals)   * Mutagen: a physical or chemical agent that causes a change in DNA (mutation), X-rays, UV light   * Teratogen: a physical or chemical agent that causes birth defects, or congenital malformation. Results from use of alcohol during pregnancy, resulting in fetal alcohol syndrome and causes changes in DNA expression.

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Describe effects of the following:

  • Alcohol Use in Pregnancy (Fetal Alcohol Syndrome)   * Alcohol use during pregnancy can have a range of negative effects on the developing fetus, including a condition known as fetal alcohol syndrome (FAS). Some common features of fetal alcohol syndrome include:   * Physical abnormalities: Children with fetal alcohol syndrome may have a characteristic set of facial features, including a small head, small eye openings, a thin upper lip, and a flat or smooth philtrum (the groove between the nose and upper lip). They may also have low birth weight, growth deficiencies, and organ malformations.   * Cognitive and behavioral problems: Children with fetal alcohol syndrome may experience a range of cognitive and behavioral problems, including developmental delays, intellectual disability, attention deficit hyperactivity disorder (ADHD), and problems with learning and memory.
  • Thalidomide   * Describe how thalidomide effects are a phenocopy     * Thalidomide is a drug that was widely prescribed to pregnant women in the late 1950s as a treatment for morning sickness. However, it was later discovered that thalidomide had severe teratogenic effects, causing a range of birth defects in the children of women who had taken the drug during pregnancy.     * The birth defects caused by thalidomide are often described as a phenocopy, which means that they resemble the effects of a genetic mutation or other naturally occurring biological process. In this case, the teratogenic effects of thalidomide mimic the effects of phocomelia, a genetic disorder in which limb development halts in the 3rd to 5th week of development.

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  • DES   * DES, or diethylstilbestrol, is a synthetic form of the hormone estrogen that was prescribed to pregnant women from the 1940s to the early 1970s to prevent miscarriage and other pregnancy complications.     * It was later discovered that DES had a range of negative effects on the health of the women who had taken it, as well as on their children. These effects included risk of reproductive problems, effects on the immune system, increased risk of breast cancer, and effects on offspring.

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  • Accutane   * Accutane (isotretinoin) is a prescription medication used to treat severe acne. However, Accutane has several potential side effects. These include teratogenic effects (birth defects), skin and mucous membrane effects (dry skin, chapped lips), psychological effects (depression, anxiety, etc), and gastrointestinal effects (nausea).     * Accutane provides too much Vitamin A, which could cause problems in a developing fetus, so it is important for women on this drug not to be pregnant.

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