T.O.C ~ Changes in DNA can produce Variation Chap. 5; Lesson 5.2 Activity: “One day the cat ate the rat”

DNA Sequences Can Change Differences, or variations, in DNA are what make one organism different from another. Humans contain 3 billion base pairs in our DNA. Only 5% are in genes that code for RNA & proteins. 99.9% of the DNA between 2 ppl are the same. What makes us unique is the .1% of variation found w/in us all. This is about 1 base in a 1,000. Genes and their interaction w/ environment determine the traits of a person. Genes produce variation b/c the amount or type of proteins they code for differ from person to person. Given the huge # of base pairs in DNA (of any organism) it is not surprising that errors occur

Hypertrichosis Also called “werewolf syndrome” or Ambras syndrome, and it affects as few as one in a billion people; and in fact, only 50 cases have been documented since the Middle Ages. People with hypertrichosis have excessive hair on the shoulders, face, and ears It happens in the 3-month fetus at the eyebrows and down to the toes. Normally, signals from the dermis send the messages to form follicles. As a follicle forms, it sends signals to prevent the area around it from also becoming a follicle, which results in the equal spacing of our five million or so follicles. Most of our body parts ignore the messages to form follicles, which explains why most of us are relatively hairless.

Progeria This genetic disorder is as rare as it is severe. The classic form of the disease, called Hutchinson-Gilford Progeria, causes accelerated aging. Most children who have progeria essentially die of age-related diseases around the age of 13, but some can live into their 20s. Death is typically caused by a heart attack or stroke. It affects as few as one per eight million live births. http://io9.com/10-unusual-genetic-mutations-in-humans-470843733

What Causes these Changes? Exposure to ultraviolet or x-rays Natural & human-made toxins Mutation (w.w) any change in DNA What Happens When an Error Occurs? Certain enzymes proofread/repair our DNA, but don’t always get the job done. When mutation occurs in a gene, the wrong amino acid may be placed in the amino acid chain for a protein. This has 3 possible outcomes: The mutation will cause no effect The effect of the mutation is minor- could be a change in the amount of melanin produced. (albino) The effect of the mutation is great- could be good, like having increased resistance to disease, or bad, causing genetic disorder or disease. Remember only 5% of human DNA is in genes. If a mutation occurs in the noncoding region of DNA, the mutation will most likely be neutral w/ no effect.

Mutations can cause Genetic Disorders A genetic disorder is a disease or condition that results from mutations that affect the normal functioning of a cell. Pedigree (w.w)- diagram of family relationships that includes two or more generations. Sometimes these disorders are inherited, from parent to offspring. Causes of Genetic Disorders: Inherited: albinism, cystic fibrosis, sickle cell disease (recessive, severe, more prevalent in Africa/Mid-East) Mutations that occur over a person’s lifetime. (most cancers) Sometimes a person carries a tendency towards a disease; such as diabetes, glaucoma, Alzheimer’s disease, or emphysema. Sometimes a person’s behavior can help to prevent a disease (i.e. smoking) http://eveloce.scienceblog.com/94/the-thousand-dollar-genome-has-arrived/ Should we be scared or amazed by this?

Cancer is a Genetic Disorder that affects the Cell Cycle. Cancer is not a single genetic disorder but more of a group of them. All cancers are characterized by uncontrolled cell division. A normal cell has a definite life cycle. Cancer cells become “immortal” by dividing indefinitely. They spread quickly & invade other tissues. Cancer involves a series of mutations. What is inherited is a mutation that is one step in the series. The disease only occurs if other mutations become present. Most are caused by mutations that occur over a person’s lifetime. Some are genetic mistake Some are caused by chemicals called carcinogens (tobacco/nicotine) Ultraviolet, nuclear radiation, & x-rays can cause cancer

5.2 Review Q’s 15 points What is a mutation? (2 points) What 3 ways can mutations effect an organism? (3 points) What effect does cancer have on the cell cycle of a cell? (2 points) What is a genetic disorder? (2 points) Name 3 causes of genetic disorders and give 1 example of each. (6 points)