MicroBio 160 1st Edition Lecture 9 Outline of Last Lecture I What is Epidemiology II The Epidemiological Approach III Epidemiological Study IV How do we Evaluate Evidence V Comparison of Disease in Different Locations VI What s the Difference VII The Effect of Bias VIII Limitations of Epidemiology IX Types of Epidemiology X The Epidemiologic Triad XI Main Causes of Cancer Outline of Current Lecture I Cancer Cases and Risk Factors II The Ames Test for Carcinogenic Potential III Environment vs Hereditary IV Diet and Cancer Risk V Radiation and Cancer VI Oncogenic Viruses and Bacteria VII How Do You Know if You Are At Risk VIII Somatic vs Inherited Cancers IX Hereditary Risk Examples X Typical Xeroderma Pigmentosum Pedigree XI Familial Retinoblastoma Pedigree Current Lecture Cancer Cases and Risk Factors Age Environmental Factors Lifestyle Factors o Tobacco Use o Alcohol use o Diet food Radiation These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Oncogenic Viruses viruses that trigger oncogenes insert their DNA into our DNA and cause mutations which can cause cancer Hereditary 63 of risk is in your own control The Ames Tests for Carcinogenic Potential Mutagenic able to cause a mutation o A mutagenic isn t necessarily a carcinogenic Carcinogenic able to cause cancer Take substance you want tested liquid form combine substance being tested with liver homogenate incubate them but bacteria on 2 different growth mediums take mutigen and add it to one of the plates add bacteria and wait to see what grows If mutagenic then may randomly create a mutation that restores histidine synthesis Take substance you want tested liquid form Combine substance being tested with liver homogenate Incubate them Put bacteria on 2 different growth mediums Take mutigen and add it to one of the plates Bottom Left 2 bacterium out of 100s that gained a mutation Right a lot of colonies more growthacquired the ability to make the histidine original substance causes mutations Large amount to small amount x axis If it takes 100 then it is less immunogenic large dose weakly carcinogenic mutagenic Environment vs Hereditary Study of people that move from 1 Top Right highly immunogenic mutagenic really high risk of developing cancer All about where the mutations country to another Hereditary stays the same environment changes o In Japan stomach cancer high colon cancer low o Opposite is true in USA Japanese immigrants move to USA o Differences begin to disappear o Children of immigrants acquire cancer risks of new location Thus environment plays a larger role than hereditary o 80 90 of cancer risk due to environment o 10 20 due to hereditary If it were strictly genetic kids would get the same ones as their parents even if they changed environments Some inherited mutations increase the risk of developing cancer to almost 100 Diet and Cancer Risks Foods contain carcinogens and anti carcinoogens Anti carcinogens in fruits may block carcinogens Epidemiologists estimate that diets play a role in 30 of all fatal cancers US higher with cancer rates and meat Radiation and Cancer consumption Different foods have different carcinogens Gamma Rays and X rays ionizing radiation is high frequency radiation with enough energy to remove an electron from an ion ionize or molecule o Ionizing radiation has enough energy to damage the DNA in cells which in turn may lead to cancer Ultraviolet Rays UV high energy UV damages DNA whereas low energy UV does not Visible light infrared rays microwaves radiofrequency radio waves extremely low frequency radiation ELF Oncogenic Viruses and Bacteria EBV Burkitts s Lymphoma Hepatitis B Liver cancer HPV Cervical cancer H Pylori Stomach cancer o H pylori causes stomach ulsers o Stomach secretes Hydrochloric acid o Can dissolve all foods you are eating o Stomach secretes mucus to keep away h pylori Hereditary and Cancer Most often used DNA repair genes There is a risk of getting breast cancer with age How do you know if you are at risk A family history that might indicate an inherited gene mutation would include two or more of the following points o Cancer in several closely related people on the same side of the family and in several generations o Cancer at younger ages than usual breast cancer in your 30 s o More than one diagnosis of cancer in the same person o Specific types of cancer that are linked to specific genes breast cancer and ovary cancer or colon cancer and endometrial cancer Somatic vs Inherited Cancers Somatic mutations occur after conception No mutation is present embryo starting to develop mutation Occur in any of the cells of the body somatic except the germ cells sperm and egg thus they are not passed onto children Inherited Mutations occur before conception Hereditary Risk Examples Recessive risk takes two bad copies of a gene o Not every person will get it o It knocks out DNA repair gene Genes affecting DNA repair o Xeroderma Pigmentosum Genes involved in Tumor Suppressor o Retinoblastoma Occur in the germ cells sperm and egg thus are passed onto children Every cell in that organism will have that mutation Can cause cancer or other diseases Typical Xeroderma Pigmentosum Pedigree Requires 2 copies of mutant gene to be inherited one from each parent recessive cancer risk syndrome o Must have one normal gene to make the protein DNA repair gene o Results in absence of DNA repair o Carriers exhibit no disease symptoms but can pass gene on to children o Each child will have a 50 chance of inheriting mutant gene from each parent overall probability is 50 x 50 25 Patients are sensitive to UV sunlight could be fatal o Suit designed by NASA o Minimal sunlight exposure leads to skin cancer o Camp Sundown in upstate NY allows kids to participate in normal recreation indoors Familial Retinoblastoma Pedigree eye cancer Red developed retinoblastoma Green symbol no signs of disease Yellow arrow son with no disease but children inherited disease o Represents the 10 that inherit but do not develop disease incomplete penetrance A non carrier child has a 1 in 20 000 chance of developing retinoblastoma In families of retinoblastoma survivors 50 of the children develop the disease 40 of retinoblastoma cases are familial the rest are sporadic no familial history Children with familial form develop multiple tumors sporadic cases typically have a single tumor If you inherit you develop multiple tumors
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